Ngram tokenizer now returns an error with invalid arguments.

[fmassot]

Fixes #2100

[codecov-commenter]

Codecov Report

Merging #2102 (d73706d) into main (3b0cbf8) will decrease coverage by 0.02%.
The diff coverage is 98.30%.

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@@            Coverage Diff             @@
##             main    #2102      +/-   ##
==========================================
- Coverage   94.39%   94.37%   -0.02%     
==========================================
  Files         321      321              
  Lines       60612    60646      +34     
==========================================
+ Hits        57213    57236      +23     
- Misses       3399     3410      +11     

Impacted Files	Coverage Δ
src/core/segment_reader.rs	90.57% <0.00%> (ø)
src/lib.rs	99.05% <ø> (ø)
src/directory/ram_directory.rs	90.50% <100.00%> (ø)
src/indexer/segment_updater.rs	94.27% <100.00%> (-1.18%)	⬇️
src/postings/serializer.rs	98.95% <100.00%> (ø)
src/snippet/mod.rs	95.44% <100.00%> (ø)
src/tokenizer/ngram_tokenizer.rs	99.06% <100.00%> (+0.11%)	⬆️

... and 2 files with indirect coverage changes

[trinity-1686a]

lgtm