qcacld-3.0: Check for NULL dereference before access

Check for NULL dereference before accessing it.

Change-Id: Id2dc5f2c0f54f0c7681d2a26a53e7190ef46aba2
CRs-Fixed: 2668241

core/dp/txrx3.0/dp_fisa_rx.c

@@ -835,13 +835,15 @@ dp_rx_fisa_flush_tcp_flow(struct dp_vdev *vdev,
 {
 	qdf_nbuf_t head_skb = fisa_flow->head_skb;
 	struct iphdr *head_skb_iph;
-	struct skb_shared_info *shinfo = skb_shinfo(head_skb);
+	struct skb_shared_info *shinfo;
 
 	if (!head_skb) {
 		dp_fisa_debug("Already flushed");
 		return;
 	}
 
+	shinfo = skb_shinfo(head_skb);
+
 	/* Update the head_skb before flush */
 	head_skb->hash = fisa_flow->flow_hash;
 	head_skb->sw_hash = 1;