Removing the redundant requirement of having "fields property with empty array" for union types with no values.

Note : Values are optionals in the Discriminated Union
Reference : http://msdn.microsoft.com/en-us/library/vstudio/dd233226(v=vs.100).aspx
Merge pull request #380 from tamizhvendan/master

Removing the redundant requirement of having "fields property with empty array"