wifi: mt76: mt7925: prevent NULL pointer dereference in mt7925_tx_check_aggr()

[ Upstream commit 83ae3a1 ]

Move the NULL check for 'sta' before dereferencing it to prevent a
possible crash.

Fixes: 44eb173 ("wifi: mt76: mt7925: add link handling in mt7925_txwi_free")
Signed-off-by: Ming Yen Hsieh <mingyen.hsieh@mediatek.com>
Link: https://patch.msgid.link/20250904030649.655436-4-mingyen.hsieh@mediatek.com
Signed-off-by: Felix Fietkau <nbd@nbd.name>
Signed-off-by: Sasha Levin <sashal@kernel.org>

Author: Ming Yen Hsieh

drivers/net/wireless/mediatek/mt76/mt7925/mac.c

@@ -845,11 +845,14 @@ static void mt7925_tx_check_aggr(struct ieee80211_sta *sta, struct sk_buff *skb,
 	bool is_8023;
 	u16 fc, tid;
 
+	if (!sta)
+		return;
+
 	link_sta = rcu_dereference(sta->link[wcid->link_id]);
 	if (!link_sta)
 		return;
 
-	if (!sta || !(link_sta->ht_cap.ht_supported || link_sta->he_cap.has_he))
+	if (!(link_sta->ht_cap.ht_supported || link_sta->he_cap.has_he))
 		return;
 
 	tid = skb->priority & IEEE80211_QOS_CTL_TID_MASK;