fix: Pressing up with all options disabled underflowing

[nathan-knight]

Previously if you had a select with all options disabled, pressing up arrow would make current < 0 so memoFlattenOptions[current] would be undefined. Multiplying len by 2 is an easy way to make sure it wraps around gracefully.

[vercel]

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🔍 Inspect: https://vercel.com/react-component/select/DWYKAXc2fHeuGXXK5B7gvxHPQJLy
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[codecov]

Codecov Report

Merging #712 (598f1c4) into master (452d917) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #712   +/-   ##
=======================================
  Coverage   99.50%   99.50%           
=======================================
  Files          25       25           
  Lines        1010     1010           
  Branches      335      335           
=======================================
  Hits         1005     1005           
  Misses          4        4           
  Partials        1        1           

Impacted Files	Coverage Δ
src/OptionList.tsx	99.28% <100.00%> (ø)

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