Fix a crash in Lint/EmptyConditionalBody

[gsamokovarov]

var =
  unless object.action value:, other:
    condition || other_condition # This is the value of `other:`, like so:
                                 # `other: condition || other_condition`
  end

The code above is tricky, because we may think condition || other_condition is the body of the condition, however the code is a valid case for the Lint/EmptyConditionalBody rule. It is equivalent to:

var =
  unless object.action value:, other: condition || other_condition
  end

However, the variable assignment is tricking CommentsHelp#find_end_line method into calling an #end method of Parser::Source::Map::Variable object. Parser::Source::Map::Variable does not respond to it. Other Parser::Source::Map subclasses also do not respond to #end methods so we need to check for its existing. Parser::Source::Map::RescueBody can be a parent node too.

[bbatsov]

Looks good. I really hope we already has some cop that advises against splitting maps in such a manner over multiple lines, as such code looks horrible.

[gsamokovarov]

This wasn't the intend of this code... The devs wanted:

var =
  unless object.action(value:, other:)
    condition || other_condition
  end

But since we're forcing them to omit the parentheses in our company, rubocop nicked them, and we ended up with the empty branch. To be honest, our devs are quite confused with this syntax and how we can omit the parentheses with it. We can do it only for the returning-value expression and the however-many-edge-cases there are. It's some tricky syntax to grok.