Reduce warning when "foundation assertions" disabled

In my project, for certain build configurations, I have foundation assertions disabled. This seems to be causing the `NSAssert()` macro to do nothing, which means that `layoutConstantUpdate` is not being used. Since this is causing a warning, would it be possible to consolidate these two lines to prevent the warning?

![screen shot 2014-01-31 at 4 58 32 pm](https://f.cloud.github.com/assets/442307/2056483/a4fc01ce-8add-11e3-9844-fdcfa769a0b9.png)