[Fix rubocop#214] Fix an error for Rails/UniqueValidationWithoutIndex

Fixes rubocop#214.

This PR fixes an error for `Rails/UniqueValidationWithoutIndex`
when a table has no column definition.

CHANGELOG.md

@@ -6,6 +6,7 @@
 
 * [#213](https://github.com/rubocop-hq/rubocop-rails/pull/213): Fix a false positive for `Rails/UniqueValidationWithoutIndex` when using conditions. ([@sunny][])
 * [#215](https://github.com/rubocop-hq/rubocop-rails/issues/215): Fix a false positive for `Rails/UniqueValidationWithoutIndex` when using Expression Indexes. ([@koic][])
+* [#214](https://github.com/rubocop-hq/rubocop-rails/issues/214): Fix an error for `Rails/UniqueValidationWithoutIndex`when a table has no column definition. ([@koic][])
 
 ## 2.5.0 (2020-03-24)
 

lib/rubocop/rails/schema_loader/schema.rb

@@ -60,7 +60,7 @@ def with_column?(name:)
 
         def build_columns(node)
           each_content(node).map do |child|
-            next unless child.send_type?
+            next unless child&.send_type?
             next if child.method?(:index)
 
             Column.new(child)
@@ -69,7 +69,7 @@ def build_columns(node)
 
         def build_indices(node)
           each_content(node).map do |child|
-            next unless child.send_type?
+            next unless child&.send_type?
             next unless child.method?(:index)
 
             Index.new(child)
@@ -79,7 +79,7 @@ def build_indices(node)
         def each_content(node)
           return enum_for(__method__, node) unless block_given?
 
-          case node.body.type
+          case node.body&.type
           when :begin
             node.body.children.each do |child|
               yield(child)

spec/rubocop/cop/rails/unique_validation_without_index_spec.rb

@@ -303,6 +303,23 @@ class Article
       end
     end
 
+    context 'when a table has no column definition' do
+      let(:schema) { <<~RUBY }
+        ActiveRecord::Schema.define(version: 2020_02_02_075409) do
+          create_table "users", force: :cascade do |t|
+          end
+        end
+      RUBY
+
+      it 'ignores it' do
+        expect_no_offenses(<<~RUBY)
+          class User
+            validates :account, uniqueness: true
+          end
+        RUBY
+      end
+    end
+
     context 'when the validation is for a relation with foreign_key: option' do
       context 'without proper index' do
         let(:schema) { <<~RUBY }