Game wont restart in the build, but works great in the editor..

UnityException: GameObject has undefined tag! at (wrapper managed-to-native) UnityEngine.GameObject:get_tag () at UnityEngine.Component.get_tag () [0x00000] in :0 at PlayerCollision.OnCollisionEnter (UnityEngine.Collision collisionInfo) [0x00000] in :0 (Filename: Line: -1)