I was exploring on recently checked out project when errors on Error Log were generated after retrieving a list of calls on a method apply() (when fetching the children of apply)

Steps to reproduce:
1. Use this command to checkout the source code svn checkout http://aima-scala.googlecode.com/svn/trunk/ aima-scala-read-only
2. Navigate to Node.scala and do Open Call Hierarchy on the first apply() of the object Node (Line 22)
3. Check on the Error Log. Lots of Error during askOption should appear.

I had no time to create a simple example to reproduce the bug so I provided steps close enough to what I actually experienced.