[Fix #902] Fix kill-region advice function

[vamega]

Prevent the advice function from causing errors when rectangle-mark-mode
is not activated.

[toctan]

rectangle-mark-mode is an interactive autoloaded compiled Lisp
function in `rect.el'.

It is bound to C-x SPC.

(rectangle-mark-mode &optional ARG)

Toggle the region as rectangular.
Activates the region if needed. Only lasts until the region is deactivated.

This definitely does not fix the problem. Every time kill-region gets called, it's going to toggle the activated region as rectangular, in effect, every kill would become rectangle kill.

[vamega]

That may be the case. I'll check when I get home today.

[vamega]

@toctan is completely right. This breaks kill-region by always making it behave as if it's in rectangel-mark-mode. Will attempt to fix correctly later.