Fix possible crash when refreshing the view while renaming inline

It is not reproducible on every machine for me, but it seems that it can
happen that DolphinView's slot slotRoleEditingFinished() is invoked
after the items have already been removed from the model. In that case,
we have to return from the slot immediately to prevent a crash.

BUG: 306147
FIXED-IN: 4.9.2