Default re-used element class name to empty string

src/text-editor-component.js

@@ -4309,7 +4309,7 @@ class NodePool {
     }
 
     if (element) {
-      element.className = className
+      element.className = className || ''
       element.styleMap.forEach((value, key) => {
         if (!style || style[key] == null) element.style[key] = ''
       })