Add a reference while cleaning up.

Author: ericsnowcurrently

Python/import.c

@@ -424,6 +424,7 @@ PyImport_Cleanup(void)
 
     if (modules == NULL)
         return; /* Already done */
+    Py_INCREF(modules);
 
     /* Delete some special variables first.  These are common
        places where user values hide and people complain when their