BACKPORT: Bluetooth: Fix potential NULL dereference in RFCOMM bind callback

(cherry picked from 951b6a0717db97ce420547222647bcc40bf1eacd)

addr can be NULL and it should not be dereferenced before NULL checking.

Signed-off-by: Jaganath Kanakkassery <jaganath.k@samsung.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Change-Id: I18bda54bb1427d9443a39a04a5c551720118dc26
Bug: 30149612