fix: handle number 0 as valid label in SingleContent

- Fix logic bug where number 0 was incorrectly excluded from has-value className
- Update condition to explicitly check null, undefined, and empty string
- Add test case for number 0 value display

Author: zombieJ

src/SelectInput/Content/SingleContent.tsx

@@ -88,7 +88,11 @@ const SingleContent = React.forwardRef<HTMLInputElement, SharedContentProps>(
       <div
         className={clsx(
           `${prefixCls}-content`,
-          displayValue && displayValue.label && `${prefixCls}-content-has-value`,
+          displayValue &&
+            displayValue.label !== null &&
+            displayValue.label !== undefined &&
+            displayValue.label !== '' &&
+            `${prefixCls}-content-has-value`,
           mergedSearchValue && `${prefixCls}-content-has-search-value`,
           hasOptionStyle && `${prefixCls}-content-has-option-style`,
           classNames?.content,

tests/Select.test.tsx

@@ -282,6 +282,16 @@ describe('Select.Basic', () => {
     expect(container.querySelector('.rc-select-content-has-value')).toBeFalsy();
   });
 
+  it('should add -content-has-value className when value is number 0', () => {
+    const { container } = render(
+      <Select value={0}>
+        <Option value={0}>0</Option>
+        <Option value="1">1</Option>
+      </Select>,
+    );
+    expect(container.querySelector('.rc-select-content-has-value')).toBeTruthy();
+  });
+
   it('should default select the right option', () => {
     const { container } = render(
       <Select defaultValue="2">