fix bug with querySelector for file listing

video_metadata/static/file_listing.js

@@ -32,12 +32,12 @@ function addContents(node, json) {
 	a.addEventListener('click', function(e) {
 		e.preventDefault();
 		let element = e.target.parentNode; // NOTE: the parent 'li' element
-		let ul_node = element.parentNode.querySelector('li > ul');
-		let div_node = element.parentNode.querySelector('li > .search_result');
+		let ul_node = element.querySelector('li > ul');
+		let div_node = element.querySelector('li > .search_result');
 
-		if (ul_node) {
+		if (ul_node != null) {
 			element.removeChild(ul_node);
-		} else if (div_node) {
+		} else if (div_node != null) {
 			element.removeChild(div_node);
 		} else {
 			if (a.dataset.is_dir == 'true') {