fix piwigo album list layout

Author: zisoft

src/imageio/storage/piwigo.c

@@ -1100,6 +1100,7 @@ void gui_init(dt_imageio_module_storage_t *self)
   // album list
   ui->album_list = dt_bauhaus_combobox_new_action(DT_ACTION(self)); // Available albums
   dt_bauhaus_widget_set_label(ui->album_list, NULL, N_("album"));
+  gtk_widget_set_hexpand(GTK_WIDGET(ui->album_list), TRUE);
   g_signal_connect(G_OBJECT(ui->album_list), "value-changed",
                    G_CALLBACK(_piwigo_album_changed), (gpointer)ui);
   gtk_widget_set_sensitive(ui->album_list, FALSE);