Malformed "other_versions" should not raise

[danielcooper]

irb(main):002:0> Semantic::Version.new("1.2.3").satisfies?("foobar")
Traceback (most recent call last):
        3: from /Users/danielcooper/.rvm/rubies/ruby-2.5.1/bin/irb:11:in `<main>'
        2: from (irb):2
        1: from /Users/danielcooper/.rvm/gems/ruby-2.5.1/gems/semantic-1.6.1/lib/semantic/version.rb:97:in `satisfies?'
NoMethodError (undefined method `strip' for nil:NilClass)

I'd expect .satisfies? to be safe with any input or to return an ArgumentError in this case.