Layout/LineEndStringConcatenationIndentation - undefined method `parent' for nil:NilClass

[snutij]

Hello 👋

Given a file foo.rb:

x = %

Which is a valid syntax:

ruby -c foo.rb
Syntax OK

---

Expected behavior

Should not trigger error.

Actual behavior

rubocop -d --only Layout/LineEndStringConcatenationIndentation foo.rb

An error occurred while Layout/LineEndStringConcatenationIndentation cop was inspecting foo.rb:1:4.
undefined method `parent' for nil:NilClass
/Users/snutij/.rbenv/versions/3.2.2/lib/ruby/gems/3.2.0/gems/rubocop-1.53.1/lib/rubocop/cop/layout/line_end_string_concatenation_indentation.rb:127:in `base_column'
/Users/snutij/.rbenv/versions/3.2.2/lib/ruby/gems/3.2.0/gems/rubocop-1.53.1/lib/rubocop/cop/layout/line_end_string_concatenation_indentation.rb:121:in `check_indented'
/Users/snutij/.rbenv/versions/3.2.2/lib/ruby/gems/3.2.0/gems/rubocop-1.53.1/lib/rubocop/cop/layout/line_end_string_concatenation_indentation.rb:90:in `on_dstr'
/Users/snutij/.rbenv/versions/3.2.2/lib/ruby/gems/3.2.0/gems/rubocop-1.53.1/lib/rubocop/cop/commissioner.rb:107:in `public_send'

Steps to reproduce the problem

In LineEndStringConcatenationIndentation the on_dstr receive a node:

(rdbg) node
s(:dstr)

Then node.children result in:

(ruby) node.children
[]

So the base_column method receive a [][0] which is nil.

rubocop/lib/rubocop/cop/layout/line_end_string_concatenation_indentation.rb

Lines 83 to 93 in aaf1c3f

	def on_dstr(node)
	return unless strings_concatenated_with_backslash?(node)
	children = node.children
	if style == :aligned && !always_indented?(node)
	check_aligned(children, 1)
	else
	check_indented(children)
	check_aligned(children, 2)
	end
	end

rubocop/lib/rubocop/cop/layout/line_end_string_concatenation_indentation.rb

Lines 120 to 124 in aaf1c3f

	def check_indented(children)
	@column_delta = base_column(children[0]) + configured_indentation_width -
	children[1].loc.column
	add_offense_and_correction(children[1], MSG_INDENT) if @column_delta != 0
	end

rubocop/lib/rubocop/cop/layout/line_end_string_concatenation_indentation.rb

Lines 126 to 133 in aaf1c3f

	def base_column(child)
	grandparent = child.parent.parent
	if grandparent&.type == :pair
	grandparent.loc.column
	else
	child.source_range.source_line =~ /\S/
	end
	end

RuboCop version

bundle exec rubocop -V
1.53.1 (using Parser 3.2.2.3, rubocop-ast 1.29.0, running on ruby 3.2.2) [arm64-darwin22]
  - rubocop-minitest 0.31.0
  - rubocop-rake 0.6.0
  - rubocop-sorbet 0.7.0