do not allowed movement when shield is empty

examples/shields/rl/sb3utils.py

@@ -24,7 +24,7 @@ class MiniGridSbShieldingWrapper(gym.core.Wrapper):
         try:
             return self.shield[self.env.get_symbolic_state()]
         except:
-            return [1.0] * 3 + [1.0] * 4
+            return [0.0] * 3 + [1.0] * 4
 
     def reset(self, *, seed=None, options=None):
         obs, infos = self.env.reset(seed=seed, options=options)