shortcuts: Fix view filtering

When adding invisible groups to the pages/columns, we were
mistakenly creating new columns because the row count
stayed at zero.

https://bugzilla.gnome.org/show_bug.cgi?id=759517

gtk/gtkshortcutssection.c

@@ -645,7 +645,7 @@ gtk_shortcuts_section_reflow_groups (GtkShortcutsSection *self)
       if (!visible)
         height = 0;
 
-      if (n_rows == 0 || n_rows + height > self->max_height)
+      if (current_column == NULL || n_rows + height > self->max_height)
         {
           GtkWidget *column;
           GtkSizeGroup *group;