Decrement reference count

[radarhere]

Resolves #6323

[nulano]

Is there any reason you sometimes used Py_DECREF instead of Py_XDECREF?

It looks to me like it might be just for PyUnicode_FromString, but I don't see anything special about that function.

[radarhere]

Just for the times when we know that the value isn't null. Looking at the documentation, I had concluded that PyUnicode_FromString doesn't ever return null, unlike PyLong_FromLong.

[nulano]

I am pretty sure that is an omission in the documentation:

https://github.com/python/cpython/blob/5e6661bce968173fa45b74fa2111098645ff609c/Objects/unicodeobject.c#L1836-L1845

I'd expect every function that can allocate memory to possibly fail and return NULL.

[radarhere]

Ok, I've pushed an update.

[hugovk]

@nulano How does this look now?

[nulano]

I've got one suggestion - I'm working on a PR to open in @radarhere's repo.

Edit: see radarhere#19

[radarhere]

Just to be clear, part of @nulano's suggestion is to remove

>>> from PIL import _imagingmorph
>>> _imagingmorph.__version
'0.1'

It's an unused part of the C API, so no objections.