Bug 2176 - add property with name == null fix.

The Preconditions.checkArgument(name != null,..) check has been added into the
addProperty(String name) method in the AbstractGeneratedTypeBuilder class.

Change-Id: I9db2b718011fa397cf1cd659ae56f8764bb8316e
Signed-off-by: pkajsa <pkajsa@cisco.com>
Merge "Bug 2176 - add property with name == null fix."