bridge: Fix a NULL dereference

Introduced by commit 12eb035b.
("bridge: Allow users to configure statistics update to OVSDB.")

Cc: Alex Wang <alexw@nicira.com>
Acked-by: Ben Pfaff <blp@nicira.com>
Signed-off-by: YAMAMOTO Takashi <yamamoto@valinux.co.jp>
ovs-vswitchd.at: Fix a comment typo

Acked-by: Ben Pfaff <blp@nicira.com>
Signed-off-by: YAMAMOTO Takashi <yamamoto@valinux.co.jp>
ovs-vswitchd.at: Avoid using GNU sed extensions

Introduced by commit 12eb035b.
("bridge: Allow users to configure statistics update to OVSDB.")

Cc: Alex Wang <alexw@nicira.com>
Acked-by: Ben Pfaff <blp@nicira.com>
Signed-off-by: YAMAMOTO Takashi <yamamoto@valinux.co.jp>