Bluetooth: msft: fix null pointer deref on msft_monitor_device_evt

msft_find_handle_data returns NULL if it can't find the handle.
Therefore, handle_data must be checked, otherwise a null pointer
is dereferenced.
Signed-off-by: Soenke Huster <soenke.huster@eknoes.de>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

net/bluetooth/msft.c

@@ -704,6 +704,8 @@ static void msft_monitor_device_evt(struct hci_dev *hdev, struct sk_buff *skb)
 		   ev->monitor_state, &ev->bdaddr);
 
 	handle_data = msft_find_handle_data(hdev, ev->monitor_handle, false);
+	if (!handle_data)
+		return;
 
 	switch (ev->addr_type) {
 	case ADDR_LE_DEV_PUBLIC: