int(request.REQUEST.get('index', 0) all in try/except. See #9918

Can't assume that request strings can be cast to int().

9918 bug is due to adding of 'index' request parameter to various edit actions of the right hand panel, to cater for Well editing (which actually edits image at specified index).

This, combined with c35bac96 causes the bug. The single commit on this branch effectively reverts c35bac96, wrapping int(index) in a try / except.

A more thorough fix will be to remove the 'index' logic from the right-hand panel where not needed.