fix(keep-alive): fix keep-alive memory leak

close #12827

src/core/vdom/create-component.ts

@@ -62,6 +62,8 @@ const componentVNodeHooks = {
       vnode, // new parent vnode
       options.children // new children
     )
+    // #12187 unset children reference after use to avoid memory leak
+    options.children = undefined
   },
 
   insert(vnode: MountedComponentVNode) {