cfg80211: check reg_rule for NULL in handle_channel_custom()

We may end up with a NULL reg_rule after the loop in
handle_channel_custom() if the bandwidth didn't fit,
check if this is the case and bail out if so.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Link: https://lore.kernel.org/r/20200221104449.3b558a50201c.I4ad3725c4dacaefd2d18d3cc65ba6d18acd5dbfe@changeid


Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Git-commit: a7ee7d44
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/jberg/mac80211-next.git


CRs-Fixed: 2743684f
Change-Id: I32731604037e8d424fa7a6440b318d874e7a7616
Signed-off-by: Vinita S. Maloo <vmaloo@codeaurora.org>