fix(service.go): handle generic errors in ListContents function

Adds error handling for generic errors in the ListContents function of
the ContentService. This ensures that all types of errors are
appropriately managed and responded to, improving the robustness and
reliability of the error handling mechanism in the service layer.

internal/app/service/service.go

@@ -200,6 +200,7 @@ func (srv *ContentService) ListContents(
 		if repository.IsContentListNotFound(err) {
 			return nil, aphgrpc.HandleNotFoundError(ctx, err)
 		}
+		return nil, aphgrpc.HandleGetError(ctx, err)
 	}
 	cntDataSlice := make([]*content.ContentCollection_Data, 0)
 	for _, cntD := range cntModel {