fix: table drag register event (Tencent#5140)

Author: Wesley-0808

packages/components/table/hooks/useDragSort.ts

@@ -64,7 +64,11 @@ export default function useDragSort(
 
   // 行拖拽排序
   const registerRowDragEvent = (element: HTMLDivElement): void => {
-    if (!isRowHandlerDraggable.value && !isRowDraggable.value) return;
+    /**
+     * fix: https://github.com/Tencent/tdesign-vue-next/issues/4985
+     * 若table内容未渲染（即element子元素为空），拖拽事件不注册
+     */
+    if (element?.children?.length === 0 && !isRowHandlerDraggable.value && !isRowDraggable.value) return;
     const dragContainer = element?.querySelector('tbody');
     if (!dragContainer) {
       console.error('tbody does not exist.');