Use Coffeescript conditional assignment shorthand

[sionleroux]

This is a really minor syntax-only change and shouldn't affect behaviour at all.

Because what we're assigning in the happy side of this condition is the same as what we're checking in its expression we can use Coffeescript's shorthand with the existential operator, i.e. instead of

a = if b? then b else c

use this:

a = b ? c

Source: https://coffeescript.org/#existential-operator

Summary

Describe the goal of this PR. Mention any related Issue numbers.

Requirements (place an x in each [ ])

• I've read and understood the Contributing Guidelines and have done my best effort to follow them.
• I've read and agree to the Code of Conduct.

[seratch]

LGTM.

Just in case:

$ coffee 
coffee> foo = "a"
'a'
coffee> bar = foo ? "b"
'a'
coffee> baz = undefined
undefined
coffee> bar = baz ? "b"
'b'

[codecov]

Codecov Report

Merging #574 into master will increase coverage by 0.25%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #574      +/-   ##
==========================================
+ Coverage   84.93%   85.19%   +0.25%     
==========================================
  Files           6        6              
  Lines         385      385              
  Branches       85       84       -1     
==========================================
+ Hits          327      328       +1     
  Misses         34       34              
+ Partials       24       23       -1     

Impacted Files	Coverage Δ
src/bot.coffee	74.50% <100.00%> (+0.98%)	⬆️

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[seratch]

@sinisterstuf Thanks for taking the time to make this PR. LGTM 👍