handle empty values collection in setValues

Author: car031

logicaldoc-core/src/main/java/com/logicaldoc/core/metadata/ExtensibleObject.java

@@ -177,10 +177,11 @@ public List<Attribute> setValues(String name, List<Object> values) {
 			removeAttribute(n);
 		}
 
+		List<Attribute> attrs = new ArrayList<>();
+		
 		if (CollectionUtils.isEmpty(values))
-			throw new IllegalArgumentException("no values have been specified");
+			return attrs;
 
-		List<Attribute> attrs = new ArrayList<>();
 		Attribute master = setValue(name, values.get(0));
 		attrs.add(master);