git-gui: Correct disappearing unstaged files.
git-gui: Correct disappearing unstaged files.

A prior commit tried to use the old index state for the old working
directory state during a UI refresh of a file.  This caused files
which were being unstaged (and thus becoming unmodified) to drop
out of the working directory side of the display, at least until
the user performed a rescan to force the UI to redisplay everything.

Signed-off-by: Shawn O. Pearce <f01032651c12a22b2103346ba96b3b6b231f9d3c@spearce.org>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git