fix: NetworkBehaviourEditor exception when using the inspector view w…

…hile in play mode (Unity-Technologies#2641)

* fix

This fixes an issue where CheckForNetworkObject would perform its check when in playmode. This only needs to perform the check when not in play mode.

* style

Updated comments to be a bit clearer on what was updated.

com.unity.netcode.gameobjects/Editor/NetworkBehaviourEditor.cs

@@ -345,8 +345,9 @@ public static Transform GetRootParentTransform(Transform transform)
         /// <param name="networkObjectRemoved">used internally</param>
         public static void CheckForNetworkObject(GameObject gameObject, bool networkObjectRemoved = false)
         {
-            // If there are no NetworkBehaviours or no gameObject, then exit early
-            if (gameObject == null || (gameObject.GetComponent<NetworkBehaviour>() == null && gameObject.GetComponentInChildren<NetworkBehaviour>() == null))
+            // If there are no NetworkBehaviours or gameObjects then exit early
+            // If we are in play mode and a user is inspecting something then exit early (we don't add NetworkObjects to something when in play mode)
+            if (EditorApplication.isPlaying || gameObject == null || (gameObject.GetComponent<NetworkBehaviour>() == null && gameObject.GetComponentInChildren<NetworkBehaviour>() == null))
             {
                 return;
             }