Conflict with gem squeel

[poc7667]

As title

  irb(main):001:0> Comment.last.impressionist_count
  D, [2014-12-04T14:49:56.638230 #59807] DEBUG -- :   Comment Load (0.6ms)  SELECT  "comments".* FROM "comments"   ORDER BY "comments"."id" DESC LIMIT 1
  E, [2014-12-04T14:49:56.675283 #59807] ERROR -- : PG::SyntaxError: ERROR:  syntax error at or near ")"
  LINE 1: SELECT DISTINCT COUNT(DISTINCT ) FROM "impressions"  WHERE "...
                                         ^
  : SELECT DISTINCT COUNT(DISTINCT ) FROM "impressions"  WHERE "impressions"."impressionable_id" = $1 AND "impressions"."impressionable_type" = $2
  ActiveRecord::StatementInvalid: PG::SyntaxError: ERROR:  syntax error at or near ")"
  LINE 1: SELECT DISTINCT COUNT(DISTINCT ) FROM "impressions"  WHERE "...
                                         ^