[Bug] sc-32142 Throw NoneType error when piperider config file is empty

[kentwelcome]

PR checklist

• [x] Ensure you have added or ran the appropriate tests for your PR.
• [x] DCO signed

What type of PR is this? Bugfix

What this PR does / why we need it: Fix NoneType error when piperider config file is empty

Which issue(s) this PR fixes: sc-32142

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

[codecov[bot]]

Codecov Report

Merging #860 (99d3813) into main (3d44e4b) will not change coverage. The diff coverage is 0.00%.

@@           Coverage Diff           @@
##             main     #860   +/-   ##
=======================================
  Coverage   47.82%   47.82%           
=======================================
  Files          71       71           
  Lines        9994     9994           
=======================================
  Hits         4780     4780           
  Misses       5214     5214           

Files Changed	Coverage Δ
piperider_cli/configuration.py	61.36% <0.00%> (ø)

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