ChannelChoiceType doesn't support multiple = false

The error

Configuration (note: is used in a Braincrafted\Bundle\BootstrapBundle\Form\Type\BootstrapCollectionType):

Error message (at /admin/block/new?class=AppBundle\Document\Block\FreeProfileBlock):

Solution

Make it possible to use the ChannelChoiceType for a single channel selection in a BootstrapCollectionType, or provide another solution. In the problem is investigated and isolated to the transformer, who doesn't support a single value.