Fix an error for Rails/ReversibleMigration when calling drop_table without any arguments

changelog/fix_error_reversible_migration.md

@@ -0,0 +1 @@
+* [#1409](https://github.com/rubocop/rubocop-rails/pull/1409): Fix an error for `Rails/ReversibleMigration` when calling `drop_table` without any arguments. ([@earlopain][])

lib/rubocop/cop/rails/reversible_migration.rb

@@ -215,8 +215,10 @@ def check_irreversible_schema_statement_node(node)
         end
 
         def check_drop_table_node(node)
+          return unless (last_argument = node.last_argument)
+
           drop_table_call(node) do
-            unless node.parent.block_type? || node.last_argument.block_pass_type?
+            unless node.parent.block_type? || last_argument.block_pass_type?
               add_offense(node, message: format(MSG, action: 'drop_table(without block)'))
             end
           end

spec/rubocop/cop/rails/reversible_migration_spec.rb

@@ -121,6 +121,10 @@ def change
     it_behaves_like 'offense', 'drop_table(without block)', <<~RUBY
       drop_table :users
     RUBY
+
+    it_behaves_like 'accepts', 'drop_table(without arguments)', <<~RUBY
+      drop_table
+    RUBY
   end
 
   context 'change_column' do