SCCON fix NPE when label is missing

enterprise-adapter/src/main/java/de/ozgcloud/eingang/enterprise/entry/FormDataMapper.java

 package de.ozgcloud.eingang.enterprise.entry;
 
+import java.util.Collections;
+import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.stream.Collectors;
@@ -54,11 +56,19 @@ public interface FormDataMapper {
 	}
 
 	default Map<String, Object> mapFormField(EntryFormDataField field) {
-		return Map.of(LABEL_KEY, field.getLabel(), VALUE_KEY, field.getValue());
+		var map = new HashMap<String, Object>();
+		map.put(LABEL_KEY, field.getLabel());
+		map.put(VALUE_KEY, field.getValue());
+
+		return Collections.unmodifiableMap(map);
 	}
 
 	default Map<String, Object> mapSubForm(EntryFormDataSubForm subForm) {
-		return Map.of(LABEL_KEY, subForm.getLabel(), VALUE_KEY, mapFormItems(subForm.getFormItems()));
+		var map = new HashMap<String, Object>();
+		map.put(LABEL_KEY, subForm.getLabel());
+		map.put(VALUE_KEY, mapFormItems(subForm.getFormItems()));
+
+		return Collections.unmodifiableMap(map);
 	}
 
 	default PostfachAddress map(de.ozgcloud.eingang.enterprise.entry.EntryData.PostfachAddress address) {