issue deleting characters using dynamic mask and eager mode

[zluipaiva]

Describe the bug

Using a dynamic mask with eager set as true, when you try to delete the content, the cursor will move to a wrong position.
This happens when the delete action causes the mask to change from one option to the other

Steps to reproduce

In the link below, type enough characters to enable the second mask option. Once using the second mask, start to delete characters. When the mask comes back to the first one, the cursor will be positioned on the next character.

Maybe it's related to #128

Reproduction link

https://codepen.io/zluipaiva/pen/MWMzgRe