debug(0) doesn't print

[alexreinking]

When adding filtering capabilities to HL_DEBUG_CODEGEN in #8627, I inadvertently broke the behavior of debug(0). These are expected to print if HL_DEBUG_CODEGEN is unset (treated as 0 with no file filters).

[mcourteaux]

I had noticed working on #8749. I'm guessing that's how you also found it?? 😄

[alexreinking]

Looks like Andrew has a fix for it in #8689