fix(parser): typescript error that reads length of undefined

[buehler]

No description provided.

[codecov-io]

Codecov Report

Merging #61 into develop will increase coverage by 0.01%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##           develop      #61      +/-   ##
===========================================
+ Coverage    89.46%   89.47%   +0.01%     
===========================================
  Files           63       63              
  Lines          940      941       +1     
  Branches       166      166              
===========================================
+ Hits           841      842       +1     
  Misses          92       92              
  Partials         7        7

Impacted Files	Coverage Δ
src/DeclarationIndex.ts	83.75% <ø> (+0.1%)	⬆️
src/TypescriptParser.ts	87.14% <ø> (ø)	⬆️
src/node-parser/traverse-ast.ts	100% <ø> (ø)	⬆️

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