Obj reached not through tree caused Segmentation fault on raw_name access

[buhl]

While tab completing in the repl on the . of a blob object accessed not through the tree I caused a segfault.
I found out the repl calls inspect.getmemebers on the object which again tries to access raw_name.
I took the check from .name property and applied to to .raw_name

This is on python 3.8.2

Before fix

>>> import os, pygit2, inspect
>>> r = pygit2.Repository("/home/user/repos/pygit2")
>>> b = r.get("855c845e538b")
>>> inspect.getmembers(b)
Segmentation fault (core dumped)

After fix

>>> import os, pygit2, inspect
>>> r = pygit2.Repository("/home/user/repos/pygit2")
>>> b = r.get("855c845e538b")
>>> inspect.getmembers(b)
[('__class__', <class '_pygit2.Blob'>), 

# ...

('short_id', '855c845'), ('size', 444379), ('type', 3), ('type_str', 'blob')]