wifi: iwlwifi: mvm: check link more carefully

Some cases of restart crashing here have been reported,
while we figure out where this is going wrong, check
the link more carefully to avoid the crash.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Gregory Greenman <gregory.greenman@intel.com>
Link: https://lore.kernel.org/r/20230830112059.2b81f52ce18e.I8f3b1962013107e2d7491d817c3349359341c6ee@changeidSigned-off-by: Johannes Berg <johannes.berg@intel.com>

drivers/net/wireless/intel/iwlwifi/mvm/mac80211.c

@@ -3883,7 +3883,8 @@ int iwl_mvm_mac_sta_state_common(struct ieee80211_hw *hw,
 
 	/* this would be a mac80211 bug ... but don't crash */
 	for_each_sta_active_link(vif, sta, link_sta, link_id) {
-		if (WARN_ON_ONCE(!mvmvif->link[link_id]->phy_ctxt)) {
+		if (WARN_ON_ONCE(!mvmvif->link[link_id] ||
+				 !mvmvif->link[link_id]->phy_ctxt)) {
 			mutex_unlock(&mvm->mutex);
 			return test_bit(IWL_MVM_STATUS_HW_RESTART_REQUESTED,
 					&mvm->status) ? 0 : -EINVAL;