gitedit.py: Use a_blob for Modified diffs
gitedit.py: Use a_blob for Modified diffs

Per the GitPython API, b_blob will be None for Working tree blobs since
the corresponding object does not exist yet. Use a_blob to get the name
for the unstaged changes.

Signed-off-by: Darren Hart (VMware) <38f9eaa30910c40b06f5a60020b1222f2a953801@infradead.org>

dvhart/gedit-git-plugin