avoid to use 0 instead of NULL

diff --git a/src/graph.c b/src/graph.c
index 792bb25..b64e3f7 100644 (file)
--- a/src/graph.c
+++ b/src/graph.c
@@ -252,7 +252,7 @@ static void draw_background_lines(cairo_t *cr,
        cairo_stroke(cr);
 
        /* back to normal line style */
-       cairo_set_dash(cr, 0, 0, 0);
+       cairo_set_dash(cr, NULL, 0, 0);
 }
 
 /* Keys: sensor identifier.