Fix line runs on until end of paragraph bug

When the tracking and/or desired width is negative the loop quits before advance > desired width and  the redundant check later on skips splitting when advance <=  desired width.
Fix pathological break occurring when there is the possibility of a wider tile later on.

Essentially only permit a worst-case (letter or clip) break when we have 1 tile on the line and we aren't under the influence of a drop caps.