Fix operation with external artifact creation

Change-Id: I728534bbc0e1c29800ae57300aa3c6a4710ac887
Issue-ID: SDC-3396
Signed-off-by: andre.schmid <andre.schmid@est.tech>
diff --git a/catalog-ui/src/app/ng2/services/component-services/component.service.ts b/catalog-ui/src/app/ng2/services/component-services/component.service.ts
index 760bfc5..3093e63 100644
--- a/catalog-ui/src/app/ng2/services/component-services/component.service.ts
+++ b/catalog-ui/src/app/ng2/services/component-services/component.service.ts
@@ -223,11 +223,11 @@
             payloadData: oldOperation.artifactData
         };
 
-        const headers = new HttpHeaders();
+
         JSON.stringify(payload);
         const payloadString = JSON.stringify(payload, null, '  ');
         const md5Result = md5(payloadString).toLowerCase();
-        headers.append('Content-MD5', btoa(md5Result));
+        const headers = new HttpHeaders().append('Content-MD5', btoa(md5Result));
 
         return this.http.post(this.baseUrl + component.getTypeUrl() + component.uuid + '/interfaces/' + newOperation.interfaceId + '/operations/' + newOperation.uniqueId + '/artifacts/' + newOperation.implementation.artifactUUID,
                 payload, {headers}