FIX skip __del__ if not defined

Author: tomMoral

loky/backend/resource_tracker.py

@@ -174,6 +174,9 @@ def ensure_running(self):
     def __del__(self):
         # ignore error due to trying to clean up child process which has already been
         # shutdown on windows See https://github.com/joblib/loky/pull/450
+        # This is only required if __del__ is defined
+        if not hasattr(self, "__del__"):
+            return
         try:
             super().__del__()
         except ChildProcessError: