test: fix renderSlot tests

packages/runtime-core/__tests__/helpers/renderSlot.spec.ts

@@ -10,8 +10,17 @@ import {
   Slot
 } from '../../src'
 import { PatchFlags } from '@vue/shared'
+import { setCurrentRenderingInstance } from '../../src/componentRenderContext'
 
 describe('renderSlot', () => {
+  beforeEach(() => {
+    setCurrentRenderingInstance({ type: {} } as any)
+  })
+
+  afterEach(() => {
+    setCurrentRenderingInstance(null)
+  })
+
   it('should render slot', () => {
     let child
     const vnode = renderSlot(