default is empty array of possible types

EDIT: on second thought, it is not a good idea

Author: guy120494

src/main/java/graphql/annotations/annotationTypes/GraphQLUnion.java

@@ -25,7 +25,7 @@
 @Target(ElementType.TYPE)
 @Retention(RetentionPolicy.RUNTIME)
 public @interface GraphQLUnion {
-    Class<?>[] possibleTypes() default {};
+    Class<?>[] possibleTypes();
 
     Class<? extends TypeResolver> typeResolver() default UnionTypeResolver.class;
 }