Fix uninitialized msec_to_next in output_repaint_timer_arm

Signed-off-by: Sergi Granell <xerpi.g.12@gmail.com>
Reviewed-by: Quentin Glidic <sardemff7+git@sardemff7.net>
diff --git a/libweston/compositor.c b/libweston/compositor.c
index fb647da..048b195 100644
--- a/libweston/compositor.c
+++ b/libweston/compositor.c
@@ -2388,7 +2388,7 @@
 	struct weston_output *output;
 	bool any_should_repaint = false;
 	struct timespec now;
-	int64_t msec_to_next;
+	int64_t msec_to_next = INT64_MAX;
 
 	weston_compositor_read_presentation_clock(compositor, &now);