More of the same

A similar case in GtkIconHelper. Here we were confusing ourselves,
and compared a icon_size against -1, although the variable is
never set to -1.

gtk/gtkiconhelper.c

@@ -876,7 +876,7 @@ _gtk_icon_helper_get_size (GtkIconHelper *self,
           width = gdk_pixbuf_animation_get_width (self->priv->animation);
           height = gdk_pixbuf_animation_get_height (self->priv->animation);
         }
-      else if (self->priv->icon_size != -1)
+      else if (self->priv->icon_size != GTK_ICON_SIZE_INVALID)
         {
           ensure_icon_size (self, context, &width, &height);
         }