mac80211: allow passing NULL to ieee80211_vif_to_wdev()
mac80211: allow passing NULL to ieee80211_vif_to_wdev()

Simply return NULL in this case, instead of crashing. This can
simplify callers that would otherwise have to check for this
explicitly.

Signed-off-by: Johannes Berg <bff32994ff0f8d048f262a8388145a71b6071bfe@intel.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs