Update iiif Manifests, exclude PDF export for externalContent

we do not have the images for external content, so we can not export PDFs for these records

indexer/export/iiif.go

@@ -871,7 +871,7 @@ func CreateIiifManifest(mythread int) {
 				//if !first {
 
 				var renderings []types.Rendering
-				if ccontext == "digizeit" {
+				if ccontext == "digizeit" && !isExternalContent {
 
 					r := types.Rendering{
 						ID:     fmt.Sprintf(config.PdfDownloadURLDigizeit, manifestData.WorkID, esLog.Log),