Minor backwards compatibility changes

[JWCook]

Updates #704.

Along with #710, this fixes some possible issues with upgrading from 0.9 to 1.0

[codecov]

Codecov Report

Merging #712 (8b030a9) into main (02c49bd) will increase coverage by 0.00%.
The diff coverage is 100.00%.

❗ Current head 8b030a9 differs from pull request most recent head 13a7ca7. Consider uploading reports for the commit 13a7ca7 to get more accurate results

@@           Coverage Diff           @@
##             main     #712   +/-   ##
=======================================
  Coverage   99.71%   99.71%           
=======================================
  Files          23       23           
  Lines        1769     1772    +3     
  Branches      265      265           
=======================================
+ Hits         1764     1767    +3     
  Partials        5        5           

Impacted Files	Coverage Δ
requests_cache/backends/sqlite.py	100.00% <ø> (ø)
requests_cache/backends/base.py	100.00% <100.00%> (ø)
requests_cache/session.py	100.00% <100.00%> (ø)

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