Crash at ScriptLanguage::_evaluate_watches due to nullptr dereference

[rxlecky]

Expression::execute is getting called when there was a parse error causing the editor to crash.

[rxlecky]

I've misinterpreted the stacktrace from JavaryGames#1 (comment). Reading it again now, the cause of the crash seems to be a nullptr dereference at https://github.com/rxlecky/godot/blob/3ac33d0ea0ca8fd8acf6bc9f707f41b7a0d368c8/core/script_language.cpp#L503

[rxlecky]

@jahd2602 I added null checks to where this issue seems to be coming from. The crash shouldn't be happening anymore so I'm closing this now.

Could you be on a lookout for ERROR: Parameter is null. in your console so we can eventually fix wherever the nullptr is coming from?