[v11.3.x] GCM: Fix error checking for GCE project getter (#95617)

GCM: Fix error checking for GCE project getter (#95613)

Appropriately check error

(cherry picked from commit 08e880a823)

Co-authored-by: Andreas Christou <andreas.christou@grafana.com>

pkg/tsdb/cloud-monitoring/cloudmonitoring.go

@@ -591,7 +591,10 @@ func (s *Service) ensureProject(ctx context.Context, dsInfo datasourceInfo, proj
 func (s *Service) getDefaultProject(ctx context.Context, dsInfo datasourceInfo) (string, error) {
 	if dsInfo.authenticationType == gceAuthentication {
 		project, err := s.gceDefaultProjectGetter(ctx, cloudMonitorScope)
-		return project, errorsource.DownstreamError(err, false)
+		if err != nil {
+			return project, errorsource.DownstreamError(err, false)
+		}
+		return project, nil
 	}
 	return dsInfo.defaultProject, nil
 }