Deleting all text leaves initial blockquote attribute

If there is a block quote at the beginning of the editor contents, and the user then selects all the contents and deletes it, the blockquote attribute is not deleted (and cannot be deleted by the user). This is what remains (as displayed by DevTools): ``` Delta {ops: Array(1)} ops: Array(1) 0: attributes: {blockquote: true} insert: "\n" [[Prototype]]: Object length: 1 [[Prototype]]: Array(0) [[Prototype]]: Object ``` What should happen: The attribute should be deleted with the rest and the result should be a single "\n".