Changing x/y axis options does not do anything in image viewer

[astrofrog]

When changing the x axis to e.g. Declination for a celestial image, the y axis should change to Right Ascension and the image should end up transposed (as in Qt glue)

[astrofrog]

This does work a little for 3D cubes but I think the issue occurs because when you change e.g. x to Declination, y stays on Declination instead of also changing, and then after that the viewer remains frozen on whatever the last valid settings were. So for a cube with x=RA, y=Dec and a v slice, changing x to v works, but then changing y to v causes the viewer to no longer work. In the Qt version we always adjust the other one if the two would be the same.