[Fix rubocop#535] Fix an error for Rails/HasManyOrHasOneDependent

Fixes rubocop#535.

This PR fixes an error for `Rails/HasManyOrHasOneDependent`
when using lambda argument and not specifying any options.

CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## master (unreleased)
 
+### Bug fixes
+
+* [#535](https://github.com/rubocop/rubocop-rails/issues/535): Fix an error for `Rails/HasManyOrHasOneDependent` when using lambda argument and not specifying any options. ([@koic][])
+
 ## 2.12.0 (2021-09-09)
 
 ### New features

lib/rubocop/cop/rails/has_many_or_has_one_dependent.rb

@@ -100,8 +100,8 @@ def valid_options_in_with_options_block?(node)
         end
 
         def contain_valid_options_in_with_options_block?(node)
-          if with_options_block(node)
-            return true if valid_options?(with_options_block(node))
+          if (options = with_options_block(node))
+            return true if valid_options?(options)
 
             return false unless node.parent
 
@@ -114,6 +114,8 @@ def contain_valid_options_in_with_options_block?(node)
         end
 
         def valid_options?(options)
+          return false if options.nil?
+
           options = options.first.children.first.pairs if options.first.kwsplat_type?
 
           return true unless options

spec/rubocop/cop/rails/has_many_or_has_one_dependent_spec.rb

@@ -20,6 +20,15 @@ class Person < ApplicationRecord
       RUBY
     end
 
+    it 'registers an offense when using lambda argument and not specifying any options' do
+      expect_offense(<<~RUBY)
+        class User < ApplicationRecord
+          has_one :articles, -> { where(active: true) }
+          ^^^^^^^ Specify a `:dependent` option.
+        end
+      RUBY
+    end
+
     it 'does not register an offense when specifying `:dependent` strategy' do
       expect_no_offenses(<<~RUBY)
         class Person < ApplicationRecord