Handle atomic blocks without entities

[makenosound]

Can happen from pasted content sometimes, and we currently expect there to be an entity for each atomic block we parse:

constructor (props) {
  super(props)
  this.entityKey = props.block.getEntityAt(0)
  this.entity = Entity.get(this.entityKey)

  this.state = {
    isSelected: false,
  }
}

[makenosound]

Related this we’ll want to handle cases when entities are created, just not in the way that we want. HTML pasted with img tags, for example, will create IMAGE entities and that’s not something we support.

This gist has a potential method for dealing with this issue: https://gist.github.com/stevensacks/86ba98facd349cee678401a030563809