Replace otherwise unused variable with function call in assertions

[rhwood]

Since the height variable is only used inside an NSAssert, and NSAsserts are disabled by default in Release builds, this change prevents four warnings (two standard, two static analysis) against a product build.

[RSully]

Thanks!

I guess it is technically possible for a release build to enable them. I hadn't considered whether this was done by default or not.

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Per Apple's doc:

Assertions are disabled if the preprocessor macro NS_BLOCK_ASSERTIONS is defined [...] Note: Not all release configurations disable assertions by default

[rhwood]

Thanks.