fix: sidebar group is collapsible even when option is not set

src/client/theme-default/components/VPSidebarGroup.vue

@@ -15,8 +15,10 @@ const props = defineProps<{
 const collapsed = ref(!!props.collapsed)
 
 function toggle() {
+  if (props.collapsible) {
     collapsed.value = !collapsed.value
   }
+}
 </script>
 
 <template>