Check against `null` and `undefined`
id serialization correctly returns null for null or undefined id values rather than 0
Better serializeId implementation that takes empty strings into consideration and fixed a logic error in isNaN(id) check
Remove redundant serialized variable. :/
Merge pull request #1038 from robmonie/id_serialization

id serialization correctly returns null for null or undefined id values ...
Merge pull request #848 from bradfol/hasmany

Bug fix: hasMany loaded as null is throwing exception
Advanced errors handling