pass a copy when opening dialog

otherwise, any changes the dialog makes will reflect in the calling
view's object

dashboard/src/components/GroupDialog.vue

@@ -53,6 +53,7 @@ async function onSubmit() {
 
 defineExpose({
   async open(g = null) {
+    g = g ? JSON.parse(JSON.stringify(g)) : null; // make a copy
     group.value = g;
     name.value = g ? g.name : '';
     formError.value = {};