iwlwifi: mvm: Fix possible NULL dereference

In __iwl_mvm_remove_time_event() check that 'te_data->vif' is NULL
before dereferencing it.

Fixes: 7b3954a1 ("iwlwifi: mvm: Explicitly stop session protection before unbinding")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Ilan Peer <ilan.peer@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/iwlwifi.20210907143156.e80e52167d93.Ie2247f43f8acb2cee6dff5b07a3947c79a772835@changeid

drivers/net/wireless/intel/iwlwifi/mvm/time-event.c

@@ -662,12 +662,13 @@ static bool __iwl_mvm_remove_time_event(struct iwl_mvm *mvm,
 					u32 *uid)
 {
 	u32 id;
-	struct iwl_mvm_vif *mvmvif = iwl_mvm_vif_from_mac80211(te_data->vif);
+	struct iwl_mvm_vif *mvmvif;
 	enum nl80211_iftype iftype;
 
 	if (!te_data->vif)
 		return false;
 
+	mvmvif = iwl_mvm_vif_from_mac80211(te_data->vif);
 	iftype = te_data->vif->type;
 
 	/*