FEAT #13195 TIME 3:20 Custom fields fixes

src/app/contentManagement/controllers/MergeController.php

src/app/customField/controllers/CustomFieldController.php

src/app/resource/controllers/ExportController.php

src/app/resource/controllers/SummarySheetController.php

src/frontend/lang/lang-en.ts

src/frontend/lang/lang-fr.ts

src/frontend/lang/lang-nl.ts