OZG-768 fix adding attachments when none before

Using exported const EMPTY_ARRAY lead to getting frozen array which did not allow to push any new elements.

goofy-client/libs/tech-shared/src/lib/resource/resource.util.ts

@@ -21,7 +21,7 @@
  * Die sprachspezifischen Genehmigungen und Beschränkungen
  * unter der Lizenz sind dem Lizenztext zu entnehmen.
  */
-import { EMPTY_ARRAY, encodeUrlForEmbedding, isNotNull } from '@goofy-client/tech-shared';
+import { encodeUrlForEmbedding, isNotNull } from '@goofy-client/tech-shared';
 import { getEmbeddedResource, getUrl, Resource, ResourceUri } from '@ngxp/rest';
 import { isNil } from 'lodash-es';
 import { ApiError } from '../tech.model';
@@ -84,7 +84,7 @@ export function getEmbeddedResources<T>(
 	linkRel: string): T[] {
 
 	if (isNil(stateResource) || isNil(stateResource.resource)) {
-		return EMPTY_ARRAY;
+		return [];
 	}
 	return getEmbeddedResource<T[]>(stateResource.resource, linkRel);
 }
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