fix(components): sync the change from vuejs/core#9012

Author: lejunyang

packages/components/src/custom/apiCustomElement.ts

@@ -366,7 +366,7 @@ export class VueElement extends BaseClass {
   protected _setAttr(key: string) {
     // ignore data- and aria- attrs
     if (key.startsWith('data-') || key.startsWith('aria-')) return;
-    let value: any = this.getAttribute(key);
+    let value: any = this.hasAttribute(key) ? this.getAttribute(key) : undefined;
     const camelKey = camelize(key);
     if (this._numberProps && this._numberProps[camelKey]) {
       value = toNumberIfValid(value);