[media] lirc_dev: avoid potential null-dereference

We have to check pointer for NULL and then dereference it.

Signed-off-by: Andy Shevchenko <[e-mail]>
Signed-off-by: Mauro Carvalho Chehab <[e-mail]>

drivers/media/rc/lirc_dev.c

···
 	if (!ir->attached)
 		return POLLERR;
 
-	poll_wait(file, &ir->buf->wait_poll, wait);
+	if (ir->buf) {
+		poll_wait(file, &ir->buf->wait_poll, wait);
 
-	if (ir->buf)
 		if (lirc_buffer_empty(ir->buf))
 			ret = 0;
 		else
 			ret = POLLIN | POLLRDNORM;
-	else
+	} else
 		ret = POLLERR;
 
 	dev_dbg(ir->d.dev, LOGHEAD "poll result = %d\n",