[IronPython] NPE inside IronPython.Compiler

[Sanghyeon Seo]

Following code, reduced from MoinMoin.util.lock, causes NPE inside
IronPython.Compiler.

MoinMoin (http://moinmoin.wikiwikiweb.de/) is a popular wiki engine
written in Python.

# lock.py
class WriteLock:
    def acquire(self):
        try:
            result = self.lock.acquire()
        finally:
            if result:
                return result
            else:
                self.lock.release()

Seo Sanghyeon