libgimp: allow NULL title for gimp_procedure_dialog_new()…
… but only when a menu label was set with gimp_procedure_set_menu_label(). In such case, this menu label is used as dialog title (with mnemonic underscore removed).
… but only when a menu label was set with gimp_procedure_set_menu_label(). In such case, this menu label is used as dialog title (with mnemonic underscore removed).