fix(resizer): check for undefined option instead of fallback

[ghiscoding]

No description provided.

[codecov]

Codecov Report

Merging #474 into master will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##            master      #474   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files          148       148           
  Lines         9534      9534           
  Branches      3311      3311           
=========================================
  Hits          9534      9534           

Impacted Files	Coverage Δ
...ules/angular-slickgrid/services/resizer.service.ts	100.00% <100.00%> (ø)

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