Crash when switching to any justified alignment on certain paragraphs

[tim-eves]

Switching to any of the justified alignments on most paragraphs works as expected. On some rare paragraphs this will case InDesign to crash.
These paragraphs have been found to be cases where the last line ends with a run of one character in length which is whitespace.

[tim-eves]

Bounds check bug discovered. We find all the whitespace from the run and then backup by one more to get the last non whitespace character to trim letter space from. In this particular case we've backuped past the begining of the run.