Folder guardian: fail on empty uid (#99465)

pkg/services/guardian/accesscontrol_guardian.go

@@ -109,23 +109,23 @@ func NewAccessControlFolderGuardianByUID(
 	ctx context.Context, cfg *setting.Cfg, folderUID string, user identity.Requester,
 	ac accesscontrol.AccessControl, dashboardService dashboards.DashboardService, foldersService folder.Service,
 ) (DashboardGuardian, error) {
-	var f *folder.Folder
+	if folderUID == "" {
-	if folderUID != "" {
+		return nil, ErrGuardianFolderNotFound.Errorf("failed to get folder by UID: folder UID is empty")
+	}
+
 	q := &folder.GetFolderQuery{
 		UID:          &folderUID,
 		OrgID:        user.GetOrgID(),
 		SignedInUser: user,
 	}
 
-		qResult, err := foldersService.Get(ctx, q)
+	f, err := foldersService.Get(ctx, q)
 	if err != nil {
 		if errors.Is(err, dashboards.ErrFolderNotFound) {
 			return nil, ErrGuardianFolderNotFound.Errorf("failed to get folder by UID: %w", err)
 		}
 		return nil, ErrGuardianGetFolderFailure.Errorf("failed to get folder by UID: %w", err)
 	}
-		f = qResult
-	}
 
 	return &accessControlFolderGuardian{
 		accessControlBaseGuardian: accessControlBaseGuardian{