Single-line if/then/end, WITHOUT else, generates OneLineConditional offense

[zach-brockway]

Offending code/output:

lib/ndb_ascii_parser.rb:70:9: C: Favor the ternary operator (?:) over if/then/else/end constructs.
        if gsub_result.nil? then warn( "Malformed alphanumeric value: '#{field}'" ) end
        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Note that the same line also triggers IfUnlessModifier, which I would actually expect in this case. On the other hand, OneLineConditional seems like it should only be triggered when there exists an "else" to become the right half of the ternary.

$ rubocop -V
0.32.1 (using Parser 2.2.2.6, running on ruby 2.2.1 x86_64-darwin14)

[bbatsov]

Yep, that's a bug.