Treat blank comments as no comment for indexes

Follow up of 1683410.

Signed-off-by: Jeremy Daer <jeremydaer@gmail.com>

activerecord/lib/active_record/connection_adapters/postgresql/schema_statements.rb

@@ -217,7 +217,7 @@ def indexes(table_name, name = nil)
               ]
             end
 
-            IndexDefinition.new(table_name, index_name, unique, columns, [], orders, where, nil, using.to_sym, comment)
+            IndexDefinition.new(table_name, index_name, unique, columns, [], orders, where, nil, using.to_sym, comment.presence)
           end.compact
         end
 

activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb

@@ -168,10 +168,6 @@ def supports_comments?
         true
       end
 
-      def supports_comments_in_create?
-        false
-      end
-
       def supports_savepoints?
         true
       end

activerecord/test/cases/comment_test.rb

@@ -5,7 +5,6 @@
 
 class CommentTest < ActiveRecord::TestCase
   include SchemaDumpingHelper
-  self.use_transactional_tests = false if current_adapter?(:Mysql2Adapter)
 
   class Commented < ActiveRecord::Base
     self.table_name = 'commenteds'
@@ -29,6 +28,10 @@ class BlankComment < ActiveRecord::Base
       t.string :empty_comment, comment: ''
       t.string :nil_comment, comment: nil
       t.string :absent_comment
+      t.index :space_comment, comment: ' '
+      t.index :empty_comment, comment: ''
+      t.index :nil_comment, comment: nil
+      t.index :absent_comment
     end
 
     Commented.reset_column_information
@@ -54,6 +57,12 @@ def test_blank_columns_created_in_block
     end
   end
 
+  def test_blank_indexes_created_in_block
+    @connection.indexes('blank_comments').each do |index|
+      assert_nil index.comment
+    end
+  end
+
   def test_add_column_with_comment_later
     @connection.add_column :commenteds, :rating, :integer, comment: 'I am running out of imagination'
     Commented.reset_column_information