Subtitles: Fix cc608 indents.

The original code was trying to be clever and indent one character
less than intended presumably to account the extra space character
that control codes also imply, but it's not clear that was ever an
appropriate thing to do.

Thanks to faginbagin@ for identifying the problem and the fix.
Refs #12051.
(cherry picked from commit 7d60440b2d790208a25ce707480f5b01657410f1)
Subtitles: Avoid trying to draw empty text or background objects.

Cherry-picked / adapted from 203db78ed2c8e9d59159d970b1eb89b5764a79f3.

Refs #12056