fix(list): Support null as a child element for ListItem (#584)

Author: gugu

Diff for: packages/list/ListItem.tsx

@@ -137,7 +137,7 @@ export default class ListItem<T extends {} = HTMLElement> extends React.Componen
   }
 
   renderChild = (child: React.ReactChild) => {
-    if (typeof child === 'string' || typeof child === 'number') {
+    if (typeof child === 'string' || typeof child === 'number' || child === null) {
       return child;
     }
 

Diff for: test/unit/list/ListItem.test.tsx

@@ -74,6 +74,16 @@ test('renders a list item with default tag', () => {
   assert.equal(wrapper.type(), 'li');
 });
 
+test('renders a list item with text content', () => {
+  const wrapper = shallow(<ListItem>Test</ListItem>);
+  assert.equal(wrapper.type(), 'li');
+});
+
+test('renders a list item with null as a child', () => {
+  const wrapper = shallow(<ListItem><div>Test</div>{null}</ListItem>);
+  assert.equal(wrapper.type(), 'li');
+});
+
 test('renders a list item with an anchor tag', () => {
   const wrapper = shallow(<ListItem tag='a'><div>Test</div></ListItem>);
   assert.equal(wrapper.type(), 'a');