Intersphinx type references are causing trouble.

Hello, when I set the type of a parameter to something available through intersphinx, e.g. `:type param: cvxopt.matrix` or `:type param: cvxopt:cvxopt.matrix` where `cvxopt` was successfully fetched via intersphinx, I get the following exception:

```
File "…/.local/lib/python3.7/site-packages/sphinx_automodapi/smart_resolver.py", line 76, in missing_reference_handler
if reftarget in inventory[prefix]['py:class']:
KeyError: 'py:class'
```

This is version 0.10 installed via pip.

Start at sphinx_automodapi/smart_resolver.py:76 and reproduce the failure using an intersphinx inventory containing cvxopt, with the parameter type forms shown in the issue. Trace how the inventory is accessed and verify that both references resolve without a KeyError.

Written by the indexing model from the issue text.