Calling save on a keyless Mapper object results in a NullPointerException: Trying to open an empty Box.

A simple example to reproduce the issue is attached along with the full stack trace.

***
Boot.scala

package bootstrap.liftweb

import root.net.liftweb.util._
import root.net.liftweb.http._
import root.net.liftweb.sitemap._
import root.net.liftweb.sitemap.Loc._
import Helpers._

import com.spiralarm.liftbug.mapperissue.model._
import root.java.sql.{Connection, DriverManager}
import root.net.liftweb.mapper.{DB, ConnectionManager, Schemifier, DefaultConnectionIdentifier, ConnectionIdentifier}

/**

• A class that's instantiated early and run. It allows the application
• to modify lift's environment

*/
class Boot {
def boot {
// where to search snippet
LiftRules.addToPackages("com.spiralarm.liftbug.mapperissue")

// Build SiteMap
val entries = Menu(Loc("Home", List("index"), "Home")) :: Nil
LiftRules.setSiteMap(SiteMap(entries:_*))
DB.defineConnectionManager(DefaultConnectionIdentifier, DBVendor)
DB.addLogFunc((query, time) => Log.debug("DBQUERY {" +query + "} time{" + time + "} ms") )
Schemifier.schemify(true,Log.infoF ,Parent,Child,ParentChild)

Log.info("Parent Child join " + ParentChild.join("parent","child"))




}
}
object DBVendor extends ConnectionManager {

// Force load the driver
Class.forName("com.mysql.jdbc.Driver")

// define methods

def newConnection(name : ConnectionIdentifier) = {
try {
Full(DriverManager.getConnection("jdbc:mysql://localhost:3306/bugs", "bugs", "bugs"))
} catch {
case e : Exception => e.printStackTrace; Empty
}
}

def releaseConnection (conn : Connection) { conn.close }
}

***
Parent.scala
package com.spiralarm.liftbug.mapperissue.model


import net.liftweb.
import net.liftweb.mapper._

class Parent extends LongKeyedMapper[Parent] with IdPK {

def getSingleton = Parent

object name extends MappedString(this,10)
}
object Parent extends Parent with LongKeyedMetaMapper[Parent]

class Child extends LongKeyedMapper[Child] with IdPK {

def getSingleton = Child

object name extends MappedString(this,10)

}
object Child extends Child with LongKeyedMetaMapper[Child]

class ParentChild extends Mapper[ParentChild] {

def getSingleton = ParentChild

object parent extends MappedLongForeignKey(this, Parent)
object child extends MappedLongForeignKey(this, Child)
object index extends MappedInt(this)

}
object ParentChild extends ParentChild with MetaMapper[ParentChild]{


def join (parent :String, child :String):Boolean = {
val p = Parent.create.name(parent).saveMe
val c = Child.create.name(parent).saveMe
join(p,c)
}


def join (parent :Parent, child :Child):Boolean = {
val list = ParentChild.findAll(By(ParentChild.parent,parent))
val i = list.isEmpty match {
case true => 0
case false => list.size
}
this.create.parent(parent).child(child).index(i).save
}

}

java.lang.NullPointerException: Trying to open an empty Box
at net.liftweb.util.EmptyBox.open_$bang(Box.scala:370)
at net.liftweb.util.EmptyBox.open_$bang(Box.scala:366)
at net.liftweb.mapper.MetaMapper$$anonfun$12.apply(MetaMapper.scala:583)
at net.liftweb.mapper.MetaMapper$$anonfun$12.apply(MetaMapper.scala:578)
at net.liftweb.mapper.DB$.use(DB.scala:305)
at net.liftweb.mapper.MetaMapper$class.save(MetaMapper.scala:577)
at com.spiralarm.liftbug.mapperissue.model.ParentChild$.save(Parent.scala:35)
at net.liftweb.mapper.Mapper$$anonfun$save$1.apply(Mapper.scala:84)
at net.liftweb.mapper.Mapper$$anonfun$save$1.apply(Mapper.scala:84)
at net.liftweb.util.ThreadGlobal.doWith(ThreadGlobal.scala:65)
at net.liftweb.mapper.Safe$.runSafe(Safe.scala:44)
at net.liftweb.mapper.Mapper$class.runSafe(Mapper.scala:50)
at com.spiralarm.liftbug.mapperissue.model.ParentChild.runSafe(Parent.scala:26)
at net.liftweb.mapper.Mapper$class.save(Mapper.scala:83)
at com.spiralarm.liftbug.mapperissue.model.ParentChild.save(Parent.scala:26)
at com.spiralarm.liftbug.mapperissue.model.ParentChild$.join(Parent.scala:51)
at com.spiralarm.liftbug.mapperissue.model.ParentChild$.join(Parent.scala:41)
at bootstrap.liftweb.Boot$$anonfun$boot$3.apply(Boot.scala:29)
at bootstrap.liftweb.Boot$$anonfun$boot$3.apply(Boot.scala:29)
at net.liftweb.util.Log4JLogger.info(Log.scala:240)
at net.liftweb.util.Log$.info(Log.scala:54)
at bootstrap.liftweb.Boot.boot(Boot.scala:29)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:585)
at net.liftweb.util.ClassHelpers$$anonfun$createInvoker$1.apply(ClassHelpers.scala:392)
at net.liftweb.util.ClassHelpers$$anonfun$createInvoker$1.apply(ClassHelpers.scala:390)
at net.liftweb.http.DefaultBootstrap$$anonfun$boot$1.apply(LiftRules.scala:909)
at net.liftweb.http.DefaultBootstrap$$anonfun$boot$1.apply(LiftRules.scala:909)
at net.liftweb.util.Full.map(Box.scala:330)
at net.liftweb.http.DefaultBootstrap$.boot(LiftRules.scala:909)
at net.liftweb.http.LiftFilter.bootLift(LiftServlet.scala:573)
at net.liftweb.http.LiftFilter.init(LiftServlet.scala:548)
at org.mortbay.jetty.servlet.FilterHolder.doStart(FilterHolder.java:97)
at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:50)
at org.mortbay.jetty.servlet.ServletHandler.initialize(ServletHandler.java:653)
at org.mortbay.jetty.servlet.Context.startContext(Context.java:140)
at org.mortbay.jetty.webapp.WebAppContext.startContext(WebAppContext.java:1239)
at org.mortbay.jetty.handler.ContextHandler.doStart(ContextHandler.java:517)
at org.mortbay.jetty.webapp.WebAppContext.doStart(WebAppContext.java:466)
at org.mortbay.jetty.plugin.Jetty6PluginWebAppContext.doStart(Jetty6PluginWebAppContext.java:124)
at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:50)
at org.mortbay.jetty.handler.HandlerCollection.doStart(HandlerCollection.java:152)
at org.mortbay.jetty.handler.ContextHandlerCollection.doStart(ContextHandlerCollection.java:156)
at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:50)
at org.mortbay.jetty.handler.HandlerCollection.doStart(HandlerCollection.java:152)
at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:50)
at org.mortbay.jetty.handler.HandlerWrapper.doStart(HandlerWrapper.java:130)
at org.mortbay.jetty.Server.doStart(Server.java:222)
at org.mortbay.component.AbstractLifeCycle.start(AbstractLifeCycle.java:50)
at org.mortbay.jetty.plugin.Jetty6PluginServer.start(Jetty6PluginServer.java:132)
at org.mortbay.jetty.plugin.AbstractJettyMojo.startJetty(AbstractJettyMojo.java:441)
at org.mortbay.jetty.plugin.AbstractJettyMojo.execute(AbstractJettyMojo.java:383)
at org.mortbay.jetty.plugin.AbstractJettyRunMojo.execute(AbstractJettyRunMojo.java:210)
at org.mortbay.jetty.plugin.Jetty6RunMojo.execute(Jetty6RunMojo.java:184)
at org.apache.maven.plugin.DefaultPluginManager.executeMojo(DefaultPluginManager.java:451)
at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeGoals(DefaultLifecycleExecutor.java:558)
at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeStandaloneGoal(DefaultLifecycleExecutor.java:512)
at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeGoal(DefaultLifecycleExecutor.java:482)
at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeGoalAndHandleFailures(DefaultLifecycleExecutor.java:330)
at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeTaskSegments(DefaultLifecycleExecutor.java:291)
at org.apache.maven.lifecycle.DefaultLifecycleExecutor.execute(DefaultLifecycleExecutor.java:142)
at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:336)
at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:129)
at org.apache.maven.cli.MavenCli.main(MavenCli.java:287)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:585)
at org.codehaus.classworlds.Launcher.launchEnhanced(Launcher.java:315)
at org.codehaus.classworlds.Launcher.launch(Launcher.java:255)
at org.codehaus.classworlds.Launcher.mainWithExitCode(Launcher.java:430)
at org.codehaus.classworlds.Launcher.main(Launcher.java:375)