weston-launch: Only store drm fd if we successfully opened and stat'ed it
diff --git a/src/weston-launch.c b/src/weston-launch.c
index 49b8964..e5301c7 100644
--- a/src/weston-launch.c
+++ b/src/weston-launch.c
@@ -333,7 +333,7 @@
 	if (len < 0)
 		return -1;
 
-	if (major(s.st_rdev) == DRM_MAJOR)
+	if (fd != -1 && major(s.st_rdev) == DRM_MAJOR)
 		wl->drm_fd = fd;
 
 	return 0;