Patch #3600941: Missing field copy in Json::Value::iterator causing infinite loop when using experimental internal map (#define JSON_VALUE_USE_INTERNAL_MAP) (contributed by Ming-Lin Kao).

src/lib_json/json_valueiterator.inl

@@ -149,6 +149,7 @@ ValueIteratorBase::copy( const SelfType &other )
 {
 #ifndef JSON_VALUE_USE_INTERNAL_MAP
    current_ = other.current_;
+   isNull_ = other.isNull_;
 #else
    if ( isArray_ )
       iterator_.array_ = other.iterator_.array_;