Safe Navigation Consistency: undefined method `type' for nil:NilClass

[swrobel]

Expected behavior

The cop should pass

Actual behavior

An error occurred while Lint/SafeNavigationConsistency cop was inspecting <file>
undefined method `type' for nil:NilClass
vendor/bundle/gems/rubocop-0.55.0/lib/rubocop/cop/lint/safe_navigation_consistency.rb:72:in `top_conditional_ancestor'
vendor/bundle/gems/rubocop-0.55.0/lib/rubocop/cop/lint/safe_navigation_consistency.rb:75:in `top_conditional_ancestor'
vendor/bundle/gems/rubocop-0.55.0/lib/rubocop/cop/lint/safe_navigation_consistency.rb:40:in `check'
vendor/bundle/gems/rubocop-0.55.0/lib/rubocop/cop/lint/safe_navigation_consistency.rb:36:in `on_csend'

Steps to reproduce the problem

Failing spec, which is a bit contrived, but illustrates the same failure that I get in my project's code with a more complex line: swrobel@12ba988

RuboCop version

$ rubocop -V
0.55.0 (using Parser 2.5.1.0, running on ruby 2.5.1 x86_64-darwin17)

cc @rrosenblum