fix owned ordered taggable bug

[kfyodor]

Hi again guys.

I got an email from a dude who ran into a nasty bug.

For example you have an ordered taggable model:

class MyTaggable < ActiveRecord::Base
  acts_as_ordered_taggable
end

and a simple user model:

class User < AR::Base
  acts_as_tagger
end

Let's open rails console:

user = User.last
my_taggable = MyTaggable.last

# this model has already been tagged before
my_taggable.tags_from(user) # => ['tag1', 'tag2', 'tag3']

I chose tags and their order to get into this block

# then you wanna change tags and their order. 
@user.tag(@my_taggable, with: "tag3, tag2", on: :tags) #=> and you got....

ActiveRecord::StatementInvalid: PG::SyntaxError: ERROR:  syntax error at or near "0"
LINE 1: SELECT "tags".* FROM 0 INNER JOIN "taggings" ON "tags"."id" ...
                             ^

Because of this "from" method which is being called from Relation class instead of Array.

Here's a fix and a test that recreates this behaviour.

[kfyodor]

@seuros Thanks for merging it quickly!

[seuros]

version 3.4.1 published