Issue #7732: Fix a crash on importing a module if a directory has the same name

Issue #7732: Fix a crash on importing a module if a directory has the same name
than a Python module (e.g. "__init__.py"): don't close the file twice.

PyFile_FromFile() does also close the file if PyString_FromString() failed. It
did already close the file on fill_file_fields() error (e.g. if the file is a
directory).