BUG: Textable attribute not working and causing exceptions

Version: 0.16.27 to latest

Are you able to reproduce the bug from the demo? Yes [ X] Yes [ ] No

What is the expected behavior? insert text block inside another text block Describe the bug detailed

when adding new block, or even when creating a new custom type, the "textable attribute is not working as expected and as described. Nothing similar was reported before,

What is the current behavior? i am getting an error when dragging and dropping the element (as you can see the images attached, I am trying on the demo locally , the added element is : ` editor.BlockManager.add('my-text-test', { label: 'Simple map block', content: { type: 'text', removable: true, content:'test',
droppable: true, highlightable:1, copyable:true, draggable: 1, editable:1, textable: 1

} })`

let me know if further details are required i will be happy to share them, thank you Descripe the bug detailed

Are you able to attach screenshots, screencasts or a live demo?

[ X] Yes (attach) [ ] No