Can't go back to space center after docking

[Peppie84]

While i was looking for #311 i found this:

KSP: 0.90 (fresh copy)
RemoteTech: 1.6.1

How to reproduce:

• start a rendezvous
• select the other satellite as target
• jump to the other satellite
• jump back and complete docking

[EXC 19:44:40.376] NullReferenceException: Object reference not set to an instance of an object
PatchedConicRenderer.OnSceneSwitch (GameScenes scn)
EventData`1[GameScenes].Fire (GameScenes data)
HighLogic.LoadScene (GameScenes scene)
AltimeterSliderButtons.returnToSpaceCenter ()
ScreenSafeUIButton.OnMouseUp (Boolean rightClick)
ScreenSafeUIButton.OnMouseUp ()
SSUICamera.DoMouseEvents ()
SSUICamera.Update ()

This exception is not thrown by RemoteTech but i think we initiate this exception.