handle empty input

[PSeitz]

closes #116

[codecov]

Codecov Report

Merging #120 (6e9b9fb) into main (7b64741) will decrease coverage by 0.06%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #120      +/-   ##
==========================================
- Coverage   89.90%   89.85%   -0.06%     
==========================================
  Files          13       13              
  Lines        2467     2473       +6     
==========================================
+ Hits         2218     2222       +4     
- Misses        249      251       +2     

Impacted Files	Coverage Δ
src/frame/compress.rs	78.94% <100.00%> (+0.52%)	⬆️

... and 1 file with indirect coverage changes