fix memery leak: '_routesKey' holds the Route reference when the route pop

@@ -107,6 +107,7 @@ class RouterReportManager<T> {
         _routesKey[routeName]?.remove(element);
         _routesKey[routeName]?.remove(element);
       }
       }
     }
     }
+    _routesKey.remove(routeName);
 
 
     keysToRemove.clear();
     keysToRemove.clear();
   }
   }