fix(core): Avoid iterator changes during Event.notify when adding or removing new event handlers

Author: d-biehl

packages/core/src/robotcode/core/event.py

@@ -65,7 +65,7 @@ def __bool__(self) -> bool:
         return len(self._listeners) > 0
 
     def __iter__(self) -> Iterator[Callable[_TParams, _TResult]]:
-        for r in self._listeners:
+        for r in list(self._listeners):
             c = r()
             if c is not None:
                 yield c