self.OnChangeMonth()
 
     def OnButton(self, evt):
-        self.cal.Destroy()
-        self.cal = None
+        if self.cal is not None:
+            self.cal.Destroy()
+            self.cal = None
 
     def OnCalSelected(self, evt):
         self.log.write('OnCalSelected: %s\n' % evt.GetDate())
 if __name__ == '__main__':
     import sys,os
     import run
-    run.main(['', os.path.basename(sys.argv[0])])
+    run.main(['', os.path.basename(sys.argv[0])] + sys.argv[1:])