fix(AlertReports): disabling value when not null option is active (#27550)

(cherry picked from commit ed9e542781)

superset-frontend/src/features/alerts/AlertReportModal.test.tsx

@@ -371,12 +371,15 @@ test('disables condition threshold if not null condition is selected', async ()
   userEvent.click(screen.getByTestId('alert-condition-panel'));
   await screen.findByText(/smaller than/i);
   const condition = screen.getByRole('combobox', { name: /condition/i });
+  const spinButton = screen.getByRole('spinbutton');
+  expect(spinButton).toHaveValue(10);
   await comboboxSelect(
     condition,
     'not null',
     () => screen.getAllByText(/not null/i)[0],
   );
-  expect(screen.getByRole('spinbutton')).toBeDisabled();
+  expect(spinButton).toHaveValue(null);
+  expect(spinButton).toBeDisabled();
 });
 
 // Content Section

superset-frontend/src/features/alerts/AlertReportModal.tsx

@@ -1417,7 +1417,8 @@ const AlertReportModal: FunctionComponent<AlertReportModalProps> = ({
               </StyledInputContainer>
               <StyledInputContainer css={noMarginBottom}>
                 <div className="control-label">
-                  {t('Value')} <span className="required">*</span>
+                  {t('Value')}{' '}
+                  {!conditionNotNull && <span className="required">*</span>}
                 </div>
                 <div className="input-container">
                   <input
@@ -1426,7 +1427,7 @@ const AlertReportModal: FunctionComponent<AlertReportModalProps> = ({
                     disabled={conditionNotNull}
                     value={
                       currentAlert?.validator_config_json?.threshold !==
-                      undefined
+                        undefined && !conditionNotNull
                         ? currentAlert.validator_config_json.threshold
                         : ''
                     }