fix: phrase query may return incorrect results if there's unknown word

[BubbleCal]

No description provided.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 85.71429% with 1 line in your changes missing coverage. Please review.

Project coverage is 78.03%. Comparing base (6016917) to head (d9f4406).
Report is 5 commits behind head on main.

Files with missing lines	Patch %	Lines
rust/lance-index/src/scalar/inverted/builder.rs	85.71%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2850      +/-   ##
==========================================
+ Coverage   78.02%   78.03%   +0.01%     
==========================================
  Files         229      229              
  Lines       70335    70357      +22     
  Branches    70335    70357      +22     
==========================================
+ Hits        54876    54905      +29     
+ Misses      12353    12348       -5     
+ Partials     3106     3104       -2     

Flag	Coverage Δ
unittests	78.03% <85.71%> (+0.01%)	⬆️

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[westonpace]

Do we have / want a test where all words are unknown?

[BubbleCal]

Do we have / want a test where all words are unknown?

good point, will add one