fix: ensure that building arrays does not happen to objects with leng…

[logaretm]

🔎 Overview

As reported in #2398, rules with length param will get treated as arrays by mistake. This PR adds an additional check to prevent trying to call map.

✔ Issues affected

closes #2398

[codecov]

Codecov Report

Merging #2399 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master    #2399   +/-   ##
=======================================
  Coverage   95.27%   95.27%           
=======================================
  Files          44       44           
  Lines        1058     1058           
  Branches      159      159           
=======================================
  Hits         1008     1008           
  Misses         50       50

Impacted Files	Coverage Δ
src/validate.ts	96.52% <100%> (ø)	⬆️

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