`model.inspect` does not properly show multi-mode object in FancyPtycho

[yoshikisd]

Enabling multiple object modes in FancyPtycho will cause model.inspect to display an empty window for the object image.

The issue stems from self.obj_view_slice; namely it fails to account for the additional dimension introduced with the multi-mode object.

[allevitan]

Even worse, the mutliple object modes don't even really work right now! It looks to me that it only works when the number of object modes matches the number of probe modes, and in that case it assumes that the object and probe modes come in pairs!