Ctrl+Z should have no effect in "Description" on newly open event dialog

I was editing an old event and found that pressing Ctrl+Z continuously 
could erase everything in the "Description" area.

IMO, when an old event dialog is open, Ctrl+Z should have NO effect.

Also notice that, on a newly open old event, Ctrl+Z is greyed out in 
"Edit" menu, but Ctrl+Z still has effect.

Should I file a bug?

Thanks :)