USB: keyspan: fix potential null pointer dereference

Move control-urb dereference to after NULL-check. There is otherwise a
risk of a possible null pointer dereference.

Was largely found by using a static code analysis program called
cppcheck.

[Johan: modify commit message somewhat ]
[gkh: remove stable tag as it's not a real problem that anyone has ever hit]
Signed-off-by: Rickard Strandqvist <rickard_strandqvist@spectrumdigital.se>
Signed-off-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/serial/keyspan.c

@@ -1535,14 +1535,14 @@ static int keyspan_usa26_send_setup(struct usb_serial *serial,
 
 	this_urb = p_priv->outcont_urb;
 
-	dev_dbg(&port->dev, "%s - endpoint %d\n", __func__, usb_pipeendpoint(this_urb->pipe));
-
 		/* Make sure we have an urb then send the message */
 	if (this_urb == NULL) {
 		dev_dbg(&port->dev, "%s - oops no urb.\n", __func__);
 		return -1;
 	}
 
+	dev_dbg(&port->dev, "%s - endpoint %d\n", __func__, usb_pipeendpoint(this_urb->pipe));
+
 	/* Save reset port val for resend.
 	   Don't overwrite resend for open/close condition. */
 	if ((reset_port + 1) > p_priv->resend_cont)