Fix small issue where variable hasn't been declared with var

[bensmiley]

[codecov-io]

Codecov Report

Merging #58 into master will not change coverage. The diff coverage is 100%.

@@           Coverage Diff           @@
##           master      #58   +/-   ##
=======================================
  Coverage   87.77%   87.77%           
=======================================
  Files          15       15           
  Lines         548      548           
  Branches       91       91           
=======================================
  Hits          481      481           
  Misses         55       55           
  Partials       12       12

Impacted Files	Coverage Δ
lib/dictionary.js	87.98% <100%> (ø)	:arrow_up:

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