White screen in 4.7.12
You don't mention your php5 version, that would be the most likely cause (i.e if it's less than 5.4).

But if the problem is seen in an apache error file and it's in the smarty file, then just give us the error and it should be clearer.

If you only updated the code files and didn't clear caches afterwards and run db updates, then you'll definitely want to do that, as per the documentation.