fix: tipFormatter should not crash with undefined value

src/Tracks/index.tsx

@@ -47,7 +47,7 @@ const Tracks: React.FC<TrackProps> = (props) => {
 
   // ========================== Render ==========================
   const tracksNode =
-    classNames.tracks || styles.tracks ? (
+      trackList?.length && (classNames.tracks || styles.tracks) ? (
       <Track
         index={null}
         prefixCls={prefixCls}

tests/Slider.test.js

@@ -662,4 +662,10 @@ describe('Slider', () => {
     const { asFragment } = render(<Slider included={false} />);
     expect(asFragment().firstChild).toMatchSnapshot();
   });
+
+  it('tipFormatter should not crash with undefined value', () => {
+    [undefined, null].forEach((value) => {
+      render(<Slider value={value} tooltip={{ open: true }} styles={{ tracks: {} }}/>);
+    });
+  });
 });