fix(generator): Treat empty schemas like Any instead of None. Thanks @forest-benchling![#417]

[dbanty]

Closes #417

[codecov-commenter]

Codecov Report

Merging #445 (0967894) into main (84247e5) will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##              main      #445   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           47        47           
  Lines         1563      1563           
=========================================
  Hits          1563      1563           

Impacted Files	Coverage Δ
openapi_python_client/parser/openapi.py	100.00% <100.00%> (ø)
...penapi_python_client/parser/properties/__init__.py	100.00% <100.00%> (ø)
openapi_python_client/parser/responses.py	100.00% <100.00%> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 84247e5...0967894. Read the comment docs.