Empty grammar results in cryptic exception

[johtso]

    def moduleFromGrammar(source, className, modname, filename):
        mod = module(modname)
        mod.__name__ = modname
        mod.__loader__ = GeneratedCodeLoader(source)
>       code = compile(source, filename, "exec")
E         File "/pymeta_generated_code/pymeta_grammar__Grammar.py", line 5
E           if Grammar.globals is not None:
E            ^
E       IndentationError: expected an indented block