[9.1] [Controls] Fix deselecting (blank) option from options list (#242036) (#242472)

# Backport

This will backport the following commits from `main` to `9.1`:
- [[Controls] Fix deselecting (blank) option from options list
(#242036)](#242036)

<!--- Backport version: 9.6.6 -->

### Questions ?
Please refer to the [Backport tool
documentation](https://github.com/sorenlouv/backport)

<!--BACKPORT [{"author":{"name":"Zac
Xeper","email":"[email protected]"},"sourceCommit":{"committedDate":"2025-11-10T19:31:00Z","message":"[Controls]
Fix deselecting (blank) option from options list (#242036)\n\n##
Summary\n\nCloses
https://github.com/elastic/kibana/issues/241750\n\nFixes an error with
deselecting a `(blank)` option from an options list.\n\nThe same error
when *selecting* the option was fixed
in\nhttps://github.com//pull/239791, but we missed fixing
it\nfor deselection.\n\n\n### Checklist\n\n- [x] [Unit or
functional\ntests](https://www.elastic.co/guide/en/kibana/master/development-tests.html)\nwere
updated or added to match the most common
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Fix deselecting (blank) option from options
list","number":242036,"url":"https://github.com/elastic/kibana/pull/242036","mergeCommit":{"message":"[Controls]
Fix deselecting (blank) option from options list (#242036)\n\n##
Summary\n\nCloses
https://github.com/elastic/kibana/issues/241750\n\nFixes an error with
deselecting a `(blank)` option from an options list.\n\nThe same error
when *selecting* the option was fixed
in\nhttps://github.com//pull/239791, but we missed fixing
it\nfor deselection.\n\n\n### Checklist\n\n- [x] [Unit or
functional\ntests](https://www.elastic.co/guide/en/kibana/master/development-tests.html)\nwere
updated or added to match the most common
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Fix deselecting (blank) option from options list (#242036)\n\n##
Summary\n\nCloses
https://github.com/elastic/kibana/issues/241750\n\nFixes an error with
deselecting a `(blank)` option from an options list.\n\nThe same error
when *selecting* the option was fixed
in\nhttps://github.com//pull/239791, but we missed fixing
it\nfor deselection.\n\n\n### Checklist\n\n- [x] [Unit or
functional\ntests](https://www.elastic.co/guide/en/kibana/master/development-tests.html)\nwere
updated or added to match the most common
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BACKPORT-->

Co-authored-by: Zac Xeper <[email protected]>

Author: kibanamachine

src/platform/plugins/shared/controls/public/controls/data_controls/options_list_control/get_options_list_control_factory.test.tsx

@@ -269,6 +269,11 @@ describe('Options List Control Api', () => {
       await waitFor(async () => {
         expect(option).toBeChecked();
       });
+
+      await userEvent.click(option);
+      await waitFor(async () => {
+        expect(option).not.toBeChecked();
+      });
     });
 
     test('clicking another option unselects "Exists"', async () => {

src/platform/plugins/shared/controls/public/controls/data_controls/options_list_control/get_options_list_control_factory.tsx

@@ -345,7 +345,7 @@ export const getOptionsListControlFactory = (): DataControlFactory<
         loadMoreSubject,
         deselectOption: (key: string | undefined) => {
           const field = api.field$.getValue();
-          if (!key || !field) {
+          if (key == null || !field) {
             api.setBlockingError(
               new Error(OptionsListStrings.control.getInvalidSelectionMessage())
             );