Bugfix: When cross sections intersections exclusively across signals are empty the communal sample doesn't index from the dataframe

[sandresen1]

No description provided.

[codecov]

Codecov Report

Merging #1261 (c51fafa) into develop (1f9e6ca) will increase coverage by 0.54%.
Report is 1 commits behind head on develop.
The diff coverage is 83.33%.

❗ Current head c51fafa differs from pull request most recent head 04e042e. Consider uploading reports for the commit 04e042e to get more accurate results

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #1261      +/-   ##
===========================================
+ Coverage    75.62%   76.17%   +0.54%     
===========================================
  Files           61       61              
  Lines         5445     5406      -39     
===========================================
  Hits          4118     4118              
+ Misses        1327     1288      -39     

Files	Coverage Δ
macrosynergy/signal/signal_return_relations.py	96.37% <83.33%> (-0.20%)	⬇️

... and 3 files with indirect coverage changes