client: tablet-shell: fallback in the lack of lockscreen icon

lockscreen, homescreen and shell launchers are falling back okay already and
only lockscreen icon was missing some way to keep the shell client running in
the absence of images. This patch fix it.

Signed-off-by: Tiago Vignatti <tiago.vignatti@intel.com>

clients/tablet-shell.c

@@ -197,11 +197,17 @@ lockscreen_draw(struct widget *widget, void *data)
 
 	cairo_set_operator(cr, CAIRO_OPERATOR_OVER);
 	icon = load_cairo_surface(key_lockscreen_icon);
+	if (icon) {
 		width = cairo_image_surface_get_width(icon);
 		height = cairo_image_surface_get_height(icon);
 		cairo_set_source_surface(cr, icon,
 			allocation.x + (allocation.width - width) / 2,
 			allocation.y + (allocation.height - height) / 2);
+	} else {
+		fprintf(stderr, "couldn't load lockscreen icon: %s\n",
+				 key_lockscreen_icon);
+		cairo_set_source_rgb(cr, 0.2, 0, 0);
+	}
 	cairo_paint(cr);
 	cairo_destroy(cr);
 	cairo_surface_destroy(icon);