Fix dashboard validation warning logic

app/assets/javascripts/monitoring/stores/actions.js

@@ -375,7 +375,7 @@ export const fetchDashboardValidationWarnings = ({ state, dispatch }) => {
     })
     .then(resp => resp.data?.project?.environments?.nodes?.[0]?.metricsDashboard)
     .then(({ schemaValidationWarnings } = {}) => {
-      const hasWarnings = schemaValidationWarnings?.length !== 0;
+      const hasWarnings = schemaValidationWarnings && schemaValidationWarnings.length !== 0;
       /**
        * The payload of the dispatch is a boolean, because at the moment a standard
        * warning message is shown instead of the warnings the BE returns

changelogs/unreleased/223159-fix-dahsboard-warning-logic.yml

+---
+title: Fix dashboard schema validation issue
+merge_request: 36577
+author:
+type: fixed

spec/frontend/monitoring/store/actions_spec.js

@@ -948,6 +948,25 @@ describe('Monitoring store actions', () => {
       );
     });
 
+    it('dispatches receiveDashboardValidationWarningsSuccess with false payload when the response is empty ', () => {
+      mockMutate.mockResolvedValue({
+        data: {
+          project: null,
+        },
+      });
+
+      return testAction(
+        fetchDashboardValidationWarnings,
+        null,
+        state,
+        [],
+        [{ type: 'receiveDashboardValidationWarningsSuccess', payload: false }],
+        () => {
+          expect(mockMutate).toHaveBeenCalledWith(mutationVariables);
+        },
+      );
+    });
+
     it('dispatches receiveDashboardValidationWarningsFailure if the warnings API call fails', () => {
       mockMutate.mockRejectedValue({});