Fix error handling

Signed-off-by: Bryan Frimin <bryan@getprobo.com>

pkg/coredata/processing_activities.go

@@ -27,12 +27,6 @@ import (
 	"go.probo.inc/probo/pkg/page"
 )
 
-type ErrNoProcessingActivitiesFound struct{}
-
-func (e ErrNoProcessingActivitiesFound) Error() string {
-	return "no processing activities found"
-}
-
 type (
 	ProcessingActivity struct {
 		ID                                   gid.GID                                          `db:"id"`

pkg/probo/processing_activity_service.go

@@ -404,7 +404,7 @@ func (s *ProcessingActivityService) ExportPDF(
 			}
 
 			if len(processingActivities) == 0 {
-				return &coredata.ErrNoProcessingActivitiesFound{}
+				return coredata.ErrResourceNotFound
 			}
 
 			organization := &coredata.Organization{}