fix: null value should not out of range (#640)

Author: zombieJ

src/common/createSlider.jsx

@@ -239,7 +239,7 @@ export default function createSlider(Component) {
     calcOffset(value) {
       const { min, max } = this.props;
       const ratio = (value - min) / (max - min);
-      return ratio * 100;
+      return Math.max(0, ratio * 100);
     }
 
     saveSlider = (slider) => {

tests/Slider.test.js

@@ -356,4 +356,9 @@ describe('Slider', () => {
       expect(handleBlur).toBeCalled();
     });
   });
+
+  it('should not be out of range when value is null', () => {
+    const wrapper = mount(<Slider value={null} min={1} max={10} />);
+    expect(wrapper.find('Track').props().length >= 0).toBeTruthy();
+  });
 });