Here's this error I have after dragging an object (parented to Main Camera) into the variable slot of another object's script (Also parented to Main Camera).

    NullReferenceException 
UnityEditor.HandleUtility+SavedCamera..ctor (UnityEngine.Camera source)

Detailed error:

System.NullReferenceException: 
  at <0x00000> <unknown method> 
  at (wrapper managed-to-native) UnityEngine.Camera:get_nearClipPlane () 
  at UnityEditor.HandleUtility+SavedCamera..ctor (UnityEngine.Camera source) [0x00000] 
  at UnityEditor.HandleUtility.PushCamera (UnityEngine.Camera camera) [0x00000] 
  at UnityEditor.SceneViewRotation.OnGUI () [0x00000] 
  at UnityEditor.SceneView.OnGUI () [0x00000] 
  at <0x00000> <unknown method> 
  at (wrapper managed-to-native) System.Reflection.MonoMethod:InternalInvoke (object,object[]) 
  at System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) [0x00000]

Any help would be awesome,

Kyle