check tensor exist before access shape

com.unity.ml-agents/Runtime/Inference/BarracudaModelExtensions.cs

             }
             else
             {
-                return (int)model.GetTensorByName(TensorNames.ContinuousActionOutputShape)[0];
+                var continuousOutputShape = model.GetTensorByName(TensorNames.ContinuousActionOutputShape);
+                return continuousOutputShape == null ? 0 : (int)continuousOutputShape[0];
             }
         }
 
             }
             else
             {
-                return (int)model.GetTensorByName(TensorNames.DiscreteActionOutputShape)[0];
+                var discreteOutputShape = model.GetTensorByName(TensorNames.DiscreteActionOutputShape);
+                return discreteOutputShape == null ? 0 : (int)discreteOutputShape[0];
             }
         }