fix header visible or hide in one `requestAnimationFrame`

src/layouts/Header.js

@@ -99,12 +99,12 @@ class HeaderView extends PureComponent {
             visible: true,
           });
         }
-        if (scrollTop > 300 && visible) {
+        else if (scrollTop > 300 && visible) {
           this.setState({
             visible: false,
           });
         }
-        if (scrollTop < 300 && !visible) {
+        else if (scrollTop < 300 && !visible) {
           this.setState({
             visible: true,
           });