[Pharo-project] Refactor: rename class give Spec bug.

I was trying to get the Manuia Memory Monitor to work in Pharo 2.0 Got it working, nothing special: just say Smalltalk vm parameterAt: xxx instead of the SmalltalkImage current vmParameterAt: xxx Some Cmd-. needed but worked. Then, I wanted to have a look at how it worked. I noticed a class named: MMMemoryUsageIndicadorMorph and wanted to rename it to MMMemoryUsageIndicatorMorph. But I got a MNU: receiver of "model:widget:" is nil. Quite annoying. Screenshot in attach. Phil