mac80211: fix NULL pointer crash in monitor frame injection TX path

This "patch to the patch" fixes a NULL pointer derefence crash in the new
intermediate software queues. The crash can be reproduced by injecting an
802.11 frame with a BSSID that does not belong to a configured vif. The
wperf tool (https://github.com/anyfi/wperf

) may be convenient for doing
this.

Signed-off-by: Johan Almbladh <ja@anyfi.net>

SVN-Revision: 44220