Describe the change

Fixes an issue where passing a truncate value of 1 results in an unhandled exception.

[2] pry(main)> Strings.truncate('data', 1)
NoMethodError: undefined method `gsub' for nil:NilClass
from /usr/home/kschiesser/.rvm/gems/ruby-2.6.3/gems/strings-ansi-0.1.0/lib/strings/ansi.rb:29:in `sanitize'
[3] pry(main)> wtf
Exception: NoMethodError: undefined method `gsub' for nil:NilClass
--
0: /usr/home/kschiesser/.rvm/gems/ruby-2.6.3/gems/strings-ansi-0.1.0/lib/strings/ansi.rb:29:in `sanitize'
1: /usr/home/kschiesser/code/strings/lib/strings/truncate.rb:103:in `display_width'
2: /usr/home/kschiesser/code/strings/lib/strings/truncate.rb:74:in `shorten'
3: /usr/home/kschiesser/code/strings/lib/strings/truncate.rb:62:in `truncate'
4: /usr/home/kschiesser/code/strings/lib/strings.rb:99:in `truncate'

vs

[2] pry(main)> Strings.truncate('data', 1)
=> "\u2026"

Why are we doing this?

Unhandled exceptions are generally bad :)
Related to piotrmurach/tty-table#20

Benefits

Better handling for all cases on Strings::Truncate

Drawbacks

None that I can see.

Requirements

Put an X between brackets on each line if you have done the item:
[x] Tests written & passing locally?
[x] Code style checked?
[x] Rebased with master branch?
[x] Documentaion updated?