Debugger: Unused instVars

Hi, there! :)

I just discovered some instance variables that seem to be unused in Squeak/Morphic:

failedProject
isolationHead

Then, there is some state that seems to be accessed in a useless way:

externalInterrupt
proceedValue (see screenshot attached)

Finally, there are some eToys-specific value holders in addition to the SystemWindow, which stores that anyway:

labelString
message

I did not look further into it but stumbled across those things. Just wanted to let you know about it. :) I could refactor that later if possible. ;)

Best,
Marcel