Prevent possible XSS when using jQuery (#18289)

In the case of misuse or misunderstanding from a developer whereby,
if `sel` can receive user-controlled data, jQuery `$(sel)` can lead to the
creation of a new element. Current usage is using hard-coded selectors
in the templates, but nobody prevents that from expanding to
user-controlled somehow.

web_src/js/features/comp/LabelEdit.js

@@ -1,7 +1,7 @@
 import {initCompColorPicker} from './ColorPicker.js';
 
 export function initCompLabelEdit(selector) {
-  if (!$(selector).length) return;
+  if (!$.find(selector).length) return;
   // Create label
   const $newLabelPanel = $('.new-label.segment');
   $('.new-label.button').on('click', () => {