Fixed error in function CPDescriptionOfObject when a JSON object property has a null value.
The function can't handle the following JSON object: {name:null}.
Also added a test case for this.
Merge pull request #1673 from mrcarlberg/handle_null_in_cp_description_of_object

Fixed error in CPDescriptionOfObject when JSON property has null value

Conflicts:
	Foundation/CPObject.j