Backspace key with Formula does not work.

[meadow-tulips]

Steps to produce:

• Open https://quilljs.com/docs/formats#embeds
• Use formula toolbar to add e = mc^2. After inserting formula in the editor..you will find cursor positioned after a space.
• Remove the space.
• Click Outside the editor to lose focus.
• Now position your cursor next to formula by clicking in the white-space after it and try removing it with backspace.

After looking into it for a long time.. realized that the selection range event listener is giving the last selectionRange index as 0 . However cursor is positioned at index 1.