[Fix rubocop#10514] Fix an error for Lint/EmptyConditionalBody

Fixes rubocop#10514.

This PR fixes an error for `Lint/EmptyConditionalBody`
when missing second `elsif` body.

changelog/fix_an_error_for_lint_empty_conditional_body.md

@@ -0,0 +1 @@
+* [#10514](https://github.com/rubocop/rubocop/issues/10514): Fix an error for `Lint/EmptyConditionalBody` when missing second `elsif` body. ([@koic][])

lib/rubocop/cop/mixin/comments_help.rb

@@ -46,17 +46,19 @@ def buffer
       # Returns the end line of a node, which might be a comment and not part of the AST
       # End line is considered either the line at which another node starts, or
       # the line at which the parent node ends.
+      # rubocop:disable Metrics/AbcSize
       def find_end_line(node)
         if node.if_type? && node.loc.else
           node.loc.else.line
         elsif (next_sibling = node.right_sibling)
           next_sibling.loc.line
         elsif (parent = node.parent)
-          parent.loc.end.line
+          parent.loc.end ? parent.loc.end.line : parent.loc.line
         else
           node.loc.end.line
         end
       end
+      # rubocop:enable Metrics/AbcSize
     end
   end
 end

spec/rubocop/cop/lint/empty_conditional_body_spec.rb

@@ -62,6 +62,18 @@
     RUBY
   end
 
+  it 'registers an offense for missing second `elsif` body without an inline comment' do
+    expect_offense(<<~RUBY)
+      if foo
+        do_foo
+      elsif bar
+        do_bar
+      elsif baz
+      ^^^^^^^^^ Avoid `elsif` branches without a body.
+      end
+    RUBY
+  end
+
   it 'registers an offense for missing `unless` body' do
     expect_offense(<<~RUBY)
       unless condition