Fix %rep ... %endmacro crash
Fix %rep ... %endmacro crash

Also improved a comment and an error message.

Distrotech/nasm,Distrotech/nasm,techkey/nasm,turingstudio/nasm,Distrotech/nasm,projedi/nasm,projedi/nasm,projedi/nasm,techkey/nasm,techkey/nasm,turingstudio/nasm,techkey/nasm,turingstudio/nasm,letolabs/nasm,letolabs/nasm,projedi/nasm,Distrotech/nasm,projedi/nasm,techkey/nasm,letolabs/nasm,turingstudio/nasm