repair: fix an uninitialized variable issue

repair: fix an uninitialized variable issue

An uninitialized variable issue reported by Coverity, it seems
the following for-loop can be exited in advance with isblock == 1,
and bp is still uninitialized.

In case of that, initialize bp as NULL in advance to avoid this.

Fixes: 1f7c7553489c ("repair: don't duplicate names in phase 6")
Fixes-coverity-id: 1476291
Signed-off-by: Gao Xiang <hsiangkao@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>