make modelmerger work with ui-config.json

modules/ui.py

@@ -1767,6 +1767,7 @@ Requested path was: {f}
     visit(txt2img_interface, loadsave, "txt2img")
     visit(img2img_interface, loadsave, "img2img")
     visit(extras_interface, loadsave, "extras")
+    visit(modelmerger_interface, loadsave, "modelmerger")
 
     if not error_loading and (not os.path.exists(ui_config_file) or settings_count != len(ui_settings)):
         with open(ui_config_file, "w", encoding="utf8") as file: