SELECT SERVERPROPERTY('ProductUpdateLevel') SHOWING NULL
As per https://msdn.microsoft.com/en-us/library/ms174396.aspx the property ProductUpdateLevel


  Applies to: SQL Server 2012 through current version in updates beginning in late 2015.


SQL Server 2012 SP1 CU7 is from November 2013, and so not sufficiently current. 

There is no SP1 cumulative update that would support pulling that information. You would need to move to Service Pack 2 with CU9 at the least.

As a side note, SQL Server 2012 SP1 was no longer supported as of July 2015. Service Pack 2 will stop being supported in January of 2017 (as detailed in the Microsoft Lifecycle Policy). You should look to upgrade to Service Pack 3 as soon as possible to remain in support.