clear frameRateMeter on window close

direct/src/showbase/ShowBase.py

@@ -478,7 +478,9 @@ class ShowBase(DirectObject.DirectObject):
 
         if win == self.win:
             self.win = None
-            self.frameRateMeter = None
+            if self.frameRateMeter:
+                self.frameRateMeter.clearWindow()
+                self.frameRateMeter = None
 
     def openDefaultWindow(self):
         # Creates the main window for the first time, without being

panda/src/framework/windowFramework.cxx

@@ -228,7 +228,10 @@ close_window() {
   _one_sided_reverse_enabled = false;
   _lighting_enabled = false;
 
-  _frame_rate_meter = (FrameRateMeter *)NULL;
+  if (_frame_rate_meter != (FrameRateMeter *)NULL) {
+    _frame_rate_meter->clear_window();
+    _frame_rate_meter = (FrameRateMeter *)NULL;
+  }
 }
 
 ////////////////////////////////////////////////////////////////////