can't parse empty fields

[paleozogt]

Using empty fields in certain contexts won't roundrip.

Here we create a field called "a" with an empty value:

Yaml::Node root;
Yaml::Node &node = root["list"].PushBack();
node["a"] = "";

std::stringstream stream;
Yaml::Serialize(root, stream);
std::cout << stream.str() << std::endl;

Yaml::Node roundtrip;
stream.seekg(0, std::ios::beg);
Yaml::Parse(roundtrip, stream);

This outputs correct yaml, but it won't parse:

list: 
  - a: 

terminate called after throwing an instance of 'Yaml::ParsingException'
  what():  Incorrect offset. Line 2: 

[paleozogt]

Oddly, increasing the size of the field name makes the problem go away.

Here we create a field called "abc" with an empty value:

Yaml::Node root;
Yaml::Node &node = root["list"].PushBack();
node["abc"] = "";

std::stringstream stream;
Yaml::Serialize(root, stream);
std::cout << stream.str() << std::endl;

Yaml::Node roundtrip;
stream.seekg(0, std::ios::beg);
Yaml::Parse(roundtrip, stream);

which outputs:

list: 
  - abc: