minor bug fix in favor of 3.1 release

[liuxuan30]

Will pick a few before releasing 3.1

1. revert a mistake, fix Bug in ZoomViewJob? #3299
2. add one more key for iOS 11 camera roll saving. fix Save picture crash in demos on iOS 11+ #3311

[codecov-io]

Codecov Report

Merging #3312 into master will not change coverage.
The diff coverage is 0%.

@@           Coverage Diff           @@
##           master    #3312   +/-   ##
=======================================
  Coverage   28.32%   28.32%           
=======================================
  Files         117      117           
  Lines       15669    15669           
  Branches      320      320           
=======================================
  Hits         4438     4438           
  Misses      11188    11188           
  Partials       43       43

Impacted Files	Coverage Δ
Source/Charts/Jobs/ZoomViewJob.swift	0% <0%> (ø)	⬆️

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