Exit when VIDIOC_STREAMON fails.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
diff --git a/yavta.c b/yavta.c
index 240b0eb..be2f40c 100644
--- a/yavta.c
+++ b/yavta.c
@@ -980,7 +980,9 @@
 	}
 
 	/* Start streaming. */
-	video_enable(dev, 1);
+	ret = video_enable(dev, 1);
+	if (ret < 0)
+		goto done;
 
 	size = 0;
 	clock_gettime(CLOCK_MONOTONIC, &start);