Fix TypeError in iexplore.downloads down_path

[JSCU-CNI]

This PR fixes an error in the iexplore.downloads function.

When container_record.ResponseHeaders does not exist or fails to be decoded, the variable down_path stays set to None. When passing None to self.target.fs.path / TargetPath we get an ugly exception.

This is fixed by properly checking if down_path is truthy before calling self.target.fs.path.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 74.90%. Comparing base (45bbc26) to head (a5addac).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #676   +/-   ##
=======================================
  Coverage   74.90%   74.90%           
=======================================
  Files         288      288           
  Lines       24115    24115           
=======================================
  Hits        18064    18064           
  Misses       6051     6051           

Flag	Coverage Δ
unittests	74.90% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.