fix deadlock at exit

direct/src/showbase/Loader.py

@@ -51,6 +51,9 @@ class Loader(DirectObject):
 
     def destroy(self):
         self.ignore(self.hook)
+        # Temp condition for old Panda.
+        if hasattr(loader, "stopThreads"):
+            self.loader.stopThreads()
         del self.base
         del self.loader
 

direct/src/showbase/ShowBase.py

@@ -388,6 +388,7 @@ class ShowBase(DirectObject.DirectObject):
         is closed cleanly, so that we free system resources, restore
         the desktop and keyboard functionality, etc.
         """
+        self.loader.destroy()
         self.graphicsEngine.removeAllWindows()
 
         if self.musicManager: