ReactNode Controller render prop return type

ReactElement excludes `null` as a valid return type from the `render` prop. However `null` is used in the docs samples to conditionally render fields from `useFieldArray`.

https://codesandbox.io/s/usefieldarray-virtual-input-v9wyw?file=/src/App.js:402-510

src/types/controller.ts

@@ -66,5 +66,5 @@ export type ControllerProps<
     field: ControllerRenderProps<TFieldValues, TName>;
     fieldState: ControllerFieldState;
     formState: UseFormStateReturn<TFieldValues>;
-  }) => React.ReactElement;
+  }) => React.ReactNode;
 } & UseControllerProps<TFieldValues, TName>;