Fixing TargetException errors caused by null objects being passed to InvokeOnError.  See: https://github.com/JamesNK/Newtonsoft.Json/issues/104
Merge branch 'master' of git://github.com/JamesNK/Newtonsoft.Json.git

Conflicts:
	Src/Newtonsoft.Json/Serialization/JsonContract.cs
After integration, re-fixing the TargetException incurred when using [OnError] and deserializing invalid json.