fix: Form.Item shaking when `help` is empty string (#33644)

* fix: empty help takes the line

* test: test case

components/form/FormItem.tsx

@@ -224,7 +224,8 @@ function FormItem<Values = any>(props: FormItemProps<Values>): React.ReactElemen
 
     const itemClassName = {
       [`${prefixCls}-item`]: true,
-      [`${prefixCls}-item-with-help`]: help || debounceErrors.length || debounceWarnings.length,
+      [`${prefixCls}-item-with-help`]:
+        (help !== undefined && help !== null) || debounceErrors.length || debounceWarnings.length,
       [`${className}`]: !!className,
 
       // Status

components/form/__tests__/index.test.js

@@ -315,7 +315,8 @@ describe('Form', () => {
     expect(wrapper.find('.ant-form-item-required')).toHaveLength(1);
   });
 
-  it('should show related className when customize help', () => {
+  describe('should show related className when customize help', () => {
+    it('normal', () => {
       const wrapper = mount(
         <Form>
           <Form.Item help="good">
@@ -324,7 +325,20 @@ describe('Form', () => {
         </Form>,
       );
 
-    expect(wrapper.find('.ant-form-item-with-help').length).toBeTruthy();
+      expect(wrapper.exists('.ant-form-item-with-help')).toBeTruthy();
+    });
+
+    it('empty string', () => {
+      const wrapper = mount(
+        <Form>
+          <Form.Item help="">
+            <input />
+          </Form.Item>
+        </Form>,
+      );
+
+      expect(wrapper.exists('.ant-form-item-with-help')).toBeTruthy();
+    });
   });
 
   it('warning when use v3 function', () => {