[EuiSelect] allow select's value to be reset with an undefined value

CHANGELOG.md

@@ -1,6 +1,7 @@
 ## [`master`](https://github.com/elastic/eui/tree/master)
 
 - Added a `size` prop to `EuiContextMenu` and added a smaller size ([#4409](https://github.com/elastic/eui/pull/4409))
+- Allowed visual state of `EuiSelect` with `hasNoInitialSelection` to be reset with `value={undefined}` ([#4428](https://github.com/elastic/eui/pull/4428))
 
 ## [`31.2.0`](https://github.com/elastic/eui/tree/v31.2.0)
 

src-docs/src/views/form_controls/select.js

@@ -10,16 +10,21 @@ export default () => {
     { value: 'option_three', text: 'Option three' },
   ];
 
-  const [value, setValue] = useState(options[1].value);
+  const [value, setValue] = useState(undefined);
 
   const onChange = (e) => {
     setValue(e.target.value);
   };
 
+  window.asdf = () => {
+    setValue(undefined);
+  }
+
   return (
     /* DisplayToggles wrapper for Docs only */
     <DisplayToggles canPrepend canAppend canReadOnly={false}>
       <EuiSelect
+        hasNoInitialSelection
         id="selectDocExample"
         options={options}
         value={value}