#14 "Remove all tags" can not be cancelled

[s3445816]

The 3 functions of "Remove all tags from Subtitle" (Bold, Underline and Italic) does not have any feature to cancel once clicked (the Close button (red X button in top right corner) does not cancel the action). This presumably applies to the "-HI's" button as well, which is supposed to remove all Hearing Impaired symbols (which is redundant since the "+HI" button does not work).

[dayglo]

have added undo support