RFR(M): 8008555: Debugging code in compiled method sometimes leaks memory

[Roland Westrelin]

> For every use of code_string you basically have this code pattern:
> 
> +  const char* str = code_string(ss.as_string());
> +  assert(str != NULL, "no string?");
> 
> Perhaps we should assert for null in code_string itself?

Thanks Christian for taking a look a this. I'll do the change you suggest.

Roland.