Fix typo to get proper error message

[0xR]

Otherwise you get: error is not defined

Issue #, if available:

Description of changes:

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov-io]

Codecov Report

Merging #175 into master will not change coverage.
The diff coverage is 0%.

@@           Coverage Diff           @@
##           master     #175   +/-   ##
=======================================
  Coverage   80.85%   80.85%           
=======================================
  Files          85       85           
  Lines        5700     5700           
  Branches      914      914           
=======================================
  Hits         4609     4609           
  Misses        932      932           
  Partials      159      159

Impacted Files	Coverage Δ
...ons/appsync-operations/helpers/helper-resolvers.js	91.89% <0%> (ø)	⬆️

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