add missing Bytes validation to term_agg

[PSeitz]

returns empty for now instead of failing like before

[codecov-commenter]

Codecov Report

Merging #2077 (d888b7d) into main (4b7c485) will decrease coverage by 0.01%.
The diff coverage is 89.18%.

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@@            Coverage Diff             @@
##             main    #2077      +/-   ##
==========================================
- Coverage   94.38%   94.38%   -0.01%     
==========================================
  Files         319      319              
  Lines       60041    60075      +34     
==========================================
+ Hits        56670    56700      +30     
- Misses       3371     3375       +4     

Impacted Files	Coverage Δ
src/aggregation/bucket/term_agg.rs	98.28% <88.23%> (-0.32%)	⬇️
src/aggregation/agg_req_with_accessor.rs	100.00% <100.00%> (ø)

... and 2 files with indirect coverage changes