Fix an error for Rails/NegateInclude when there is no receiver

Author: fatkodima

changelog/fix_error_for_negate_include_without_receiver.md

@@ -0,0 +1 @@
+* [#920](https://github.com/rubocop/rubocop-rails/pull/920): Fix an error for `Rails/NegateInclude` when there is no receiver. ([@fatkodima][])

lib/rubocop/cop/rails/negate_include.rb

@@ -26,7 +26,7 @@ class NegateInclude < Base
         RESTRICT_ON_SEND = %i[!].freeze
 
         def_node_matcher :negate_include_call?, <<~PATTERN
-          (send (send $_ :include? $_) :!)
+          (send (send $!nil? :include? $_) :!)
         PATTERN
 
         def on_send(node)

spec/rubocop/cop/rails/negate_include_spec.rb

@@ -12,6 +12,12 @@
     RUBY
   end
 
+  it 'does not register an offense when using `!include?` without receiver' do
+    expect_no_offenses(<<~RUBY)
+      !include?(2)
+    RUBY
+  end
+
   it 'does not register an offense when using `include?` or `exclude?`' do
     expect_no_offenses(<<~RUBY)
       array.include?(2)