Fix lag when swapping between settings and design options

packages/builder/src/components/userInterface/PropertyGroup.svelte

@@ -14,6 +14,7 @@
 </script>
 
 <DetailSummary {name} on:open show={open} thin>
+  {#if open}
     <div>
       {#each properties as props}
         <PropertyControl
@@ -25,6 +26,7 @@
           props={{ ...excludeProps(props, ['control', 'label']) }} />
       {/each}
     </div>
+  {/if}
 </DetailSummary>
 
 <style>