handle exception in Rails/RedundantReceiverInWithOptions with empty body

CHANGELOG.md

@@ -2,6 +2,9 @@
 
 ## master (unreleased)
 
+### Bug fixes
+* [#6855](https://github.com/rubocop-hq/rubocop/pull/6855): Fix an exception in `Rails/RedundantReceiverInWithOptions` when the body is empty. ([@ericsullivan][])
+
 ### Changes
 
 * [#5977](https://github.com/rubocop-hq/rubocop/issues/5977): Warn for Performance Cops. ([@koic][])
@@ -3882,3 +3885,4 @@
 [@elmasantos]: https://github.com/elmasantos
 [@luciamo]: https://github.com/luciamo
 [@dirtyharrycallahan]: https://github.com/dirtyharrycallahan
+[@ericsullivan]: https://github.com/ericsullivan

lib/rubocop/cop/rails/redundant_receiver_in_with_options.rb

@@ -81,6 +81,7 @@ class RedundantReceiverInWithOptions < Cop
 
         def on_block(node)
           with_options?(node) do |arg, body|
+            return if body.nil?
             return unless all_block_nodes_in(body).count.zero?
 
             send_nodes = all_send_nodes_in(body)

spec/rubocop/cop/rails/redundant_receiver_in_with_options_spec.rb

@@ -87,12 +87,20 @@ class Account < ApplicationRecord
         end
       RUBY
     end
+
+    it 'does not register an offense when empty' do
+      expect_no_offenses(<<-RUBY.strip_indent)
+        with_options options: false do |merger|
+        end
+      RUBY
+    end
   end
 
   context 'rails <= 4.1' do
     let(:rails_version) { 4.1 }
 
-    it 'registers an offense when using explicit receiver in `with_options`' do
+    it 'does not register an offense when using explicit receiver in ' \
+       '`with_options`' do
       expect_no_offenses(<<-RUBY.strip_indent)
         class Account < ApplicationRecord
           with_options dependent: :destroy do |assoc|