fix(streams): Handle nil record(s) returned by aws-sdk-go

[mumoshu]

Ref #27

[codecov-io]

Codecov Report

Merging #28 into master will decrease coverage by 0.84%.
The diff coverage is 0%.

@@            Coverage Diff             @@
##           master      #28      +/-   ##
==========================================
- Coverage   33.89%   33.05%   -0.85%     
==========================================
  Files           4        4              
  Lines         118      121       +3     
==========================================
  Hits           40       40              
- Misses         71       74       +3     
  Partials        7        7

Impacted Files	Coverage Δ
streams/client.go	24.39% <0%> (-0.93%)	⬇️

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[mumoshu]

Closing this in favor of #31. I've consolidated this into #31 and added tests there.