Prevent viewbox auto-scaling to items that are not in the same scene.
Prevent viewbox auto-scaling to items that are not in the same scene.

This can happen when an item that was previously added to the viewbox
is then removed using scene.removeItem().

campagnola/acq4,meganbkratz/acq4,acq4/acq4,meganbkratz/acq4,meganbkratz/acq4,campagnola/acq4,pbmanis/acq4,pmaunz/pyqtgraph,pbmanis/acq4,pbmanis/acq4,acq4/acq4,campagnola/acq4,meganbkratz/acq4,campagnola/acq4,acq4/acq4,pmaunz/pyqtgraph,pbmanis/acq4,acq4/acq4