Under certain circumstances, the Scintilla editor crashes after it has been closed in OS X. The crash log shows that the idleTriggered: method was called. I think the problem is that there is still a repeating idleTimer scheduled before everything is destroyed/released and it fires afterwards.
Perhaps the ScintillaCocoa::~ScintillaCocoa() destructor needs a SetIdle(false) as well. That seems to clear up the problem for me.