- added null pointer validation to any relevant exported function. In most cases null pointers were already being treated as 'do nothing', but there's several places where this can make the code silently fail so in these cases a VM exception will be raised, once the VM's exception handling has been repaired to provide useful diagnostics. (Right now all it does is catch the exception, print a useless message and return to the caller as if nothing has happened.)

src/p_actionfunctions.cpp

@@ -247,7 +247,7 @@ DEFINE_ACTION_FUNCTION(AActor, CheckClass)
 		PARAM_BOOL_DEF	(match_superclass);
 
 		self = COPY_AAPTR(self, pick_pointer);
-		if (self == NULL)
+		if (self == nullptr || checktype == nullptr)
 		{
 			ret->SetInt(false);
 		}