Handle null config

[alextes]

Seems prettier sometimes resolves with its options being null which blows up our 'resolve with defaults’ function. This makes sure we default prettierOptions to being an empty object.

Fixes #9

[codecov[bot]]

Codecov Report

Merging #20 into master will increase coverage by 0.03%. The diff coverage is 100%.

@@            Coverage Diff             @@
##           master      #20      +/-   ##
==========================================
+ Coverage   98.03%   98.07%   +0.03%     
==========================================
  Files           2        2              
  Lines          51       52       +1     
==========================================
+ Hits           50       51       +1     
  Misses          1        1

Impacted Files	Coverage Δ
src/index.js	98.03% <100%> (+0.03%)	:arrow_up:

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[andrewmiller1]

@hugomrdias Is it possible to merge this?

[fifn2]

Yeah I'm getting the Cannot set property 'useTabs' of null thing

[codecov-io]

Codecov Report

Merging #20 into master will increase coverage by 0.03%. The diff coverage is 100%.

@@            Coverage Diff             @@
##           master      #20      +/-   ##
==========================================
+ Coverage   98.03%   98.07%   +0.03%     
==========================================
  Files           2        3       +1     
  Lines          51       52       +1     
==========================================
+ Hits           50       51       +1     
  Misses          1        1

Impacted Files	Coverage Δ
src/index.js	98% <100%> (ø)	:arrow_up:
config.js	100% <0%> (ø)

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Continue to review full report at Codecov.

Legend - Click here to learn more Δ = absolute <relative> (impact), ø = not affected, ? = missing data Powered by Codecov. Last update 2e37e73...f076466. Read the comment docs.

[alextes]

Looking at this PR I notice it's actually pretty invasive. Not sure what I was thinking 🤔 . Normally I PR these things in parallel so they are optional to accept.

If someone shows up, let me if you'd like me to drop anything.