"qemu-system-arm -machine virt -cpu cortex-a9" error message includes a lot of "(null)"s

$ ./build/x86/qemu-system-arm -machine virt -cpu cortex-a9
qemu-system-arm: Invalid CPU model: cortex-a9
The valid models are: cortex-a7, cortex-a15, (null), (null), (null), (null), (null), (null), (null), (null), (null), (null), (null), max

I think it's printing a "(null)" entry for every aarch64 CPU. It should instead leave those out. Bug introduced by commit fa8c6177.