segfault on accessing `PyCall.inspect.mod_dict`

using PyCall `v1.92.1`

```julia
import PyCall
PyCall.inspect.mod_dict
```

segfaults.

(Originally from https://github.com/JuliaPy/PyCall.jl/issues/754#issuecomment-597896361)

Start by reproducing the Julia snippet with PyCall v1.92.1, focusing on access to PyCall.inspect.mod_dict. Trace the failure from that access through the PyCall/Python interoperability boundary; done means the same expression no longer segfaults.

索引モデルが issue の本文から書いたものです。