[gtk+/gtk-3-22] iconhelper: Show error if fail to load placeholder icon

[Robert Ancell <rancell src gnome org>]

commit b21bb316bde66042fc8437513776913774abbf95
Author: Robert Ancell <robert ancell canonical com>
Date:   Thu Jun 8 11:29:09 2017 +1200

    iconhelper: Show error if fail to load placeholder icon

 gtk/gtkiconhelper.c |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)
---
diff --git a/gtk/gtkiconhelper.c b/gtk/gtkiconhelper.c
index 7ef33ae..f6e3e29 100644
--- a/gtk/gtkiconhelper.c
+++ b/gtk/gtkiconhelper.c
@@ -483,13 +483,15 @@ ensure_surface_for_gicon (GtkIconHelper    *self,
 
   if (destination == NULL)
     {
+      GError *error = NULL;
       destination = gtk_icon_theme_load_icon (icon_theme,
                                               "image-missing",
                                               width,
                                               flags | GTK_ICON_LOOKUP_USE_BUILTIN | 
GTK_ICON_LOOKUP_GENERIC_FALLBACK,
-                                              NULL);
+                                              &error);
       /* We include this image as resource, so we always have it available or
        * the icontheme code is broken */
+      g_assert_no_error (error);
       g_assert (destination);
       symbolic = FALSE;
     }