Fix dialog autosizing to accomodate for hline

dialog will conditionally ignore the --hline option if not enough space
was available to accomodate for the text width. Traditionally the width
of the widget had to be 10 wider than the text. Recent updates to dialog
have changed the requirement to be at least 12 wider than the hline text
else the hline text is not rendered at the bottom of the widget.

Sponsored by: Smule, Inc.