Choice type multiple expand problem

[Thiblef]

Since the 1.1.0 RC, all choice types with options multiple=true and expanded=true doesn't works correctly. It works with options multiple=true and expanded=false.

When we save the block containing the type, checkboxes with value off disappear.
If the first checkbox isn't selected and others selected an invalid form error is throw.
I think there's a transform problem.

[ghost]

I reproduced it on http://admin.openorchestra.1-1.inte .

1. On any content type, add a new field :
   -> Type : Choice
   -> Required : no
   -> Multiple : yes
   -> Expanded : yes
   -> Choices : 1,2,3,4
   -> Default : 1

2. Create a new content from this type and check "yes" for choice 2, "no" for other choices.

3. Submit and see the problem.

[alavieille]

This is fixed in #1767 and #1763