Bluetooth: 6lowpan: Make sure skb exists before accessing it

We need to make sure that the saved skb exists when
resuming or suspending a CoC channel. This can happen if
initial credits is 0 when channel is connected.
Signed-off-by: Jukka Rissanen <jukka.rissanen@linux.intel.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

net/bluetooth/6lowpan.c

@@ -950,6 +950,9 @@ static void chan_suspend_cb(struct l2cap_chan *chan)
 
 	BT_DBG("chan %p conn %p skb %p", chan, chan->conn, skb);
 
+	if (!skb)
+		return;
+
 	lowpan_cb(skb)->status = -EAGAIN;
 }
 
@@ -959,6 +962,9 @@ static void chan_resume_cb(struct l2cap_chan *chan)
 
 	BT_DBG("chan %p conn %p skb %p", chan, chan->conn, skb);
 
+	if (!skb)
+		return;
+
 	lowpan_cb(skb)->status = 0;
 }