minor fix

index.html

@@ -336,8 +336,6 @@ $$$('#group_by', 'change', (e) => {
     }
 
     switch (e.target.value) {
-        default:
-            $('#subcategory').options.length = 0;
         case 'none':
             $('#subcategory').classList.add('inactive');
             $('#subcategory').disabled = true;
@@ -348,6 +346,7 @@ $$$('#group_by', 'change', (e) => {
             $('#subcategory').disabled = false;
             break;
     }
+    $('#subcategory').options.length = 0;
 
     for (let [key, value] of Object.entries(results)) {
         let option = new Option(`${key} (${value})`, key);