Signature pad fromData fails due to division by zero

[samvimes01]

Do you want to request a feature or report a bug?
Report a bug when signature is not drawn.

What is the current behavior?
Signature Pad fails to draw a signature on a canvas.
For example this signature was generated by another old library and stored in the DB (like this http://keith-wood.name/signature.html).

const points = [{"points":[{"x":54.4,"y":10.9,"color":"black","pressure":0.5},{"x":54.4,"y":10.9,"color":"black","pressure":0.5},{"x":54.2,"y":10.9,"color":"black","pressure":0.5},{"x":53.8,"y":10.9,"color":"black","pressure":0.5},{"x":52.6,"y":10.9,"color":"black","pressure":0.5},{"x":51,"y":10.9,"color":"black","pressure":0.5},{"x":49.4,"y":10.9,"color":"black","pressure":0.5},{"x":47.8,"y":11,"color":"black","pressure":0.5},{"x":46.6,"y":11.2,"color":"black","pressure":0.5},{"x":46,"y":11.7,"color":"black","pressure":0.5},{"x":45.6,"y":12.3,"color":"black","pressure":0.5},{"x":45.4,"y":13.4,"color":"black","pressure":0.5},{"x":45,"y":15,"color":"black","pressure":0.5},{"x":44.6,"y":16.7,"color":"black","pressure":0.5},{"x":44.4,"y":18.4,"color":"black","pressure":0.5},{"x":44.2,"y":20.1,"color":"black","pressure":0.5},{"x":44,"y":21.3,"color":"black","pressure":0.5},{"x":44.2,"y":22,"color":"black","pressure":0.5},{"x":44.8,"y":22.5,"color":"black","pressure":0.5},{"x":46,"y":22.8,"color":"black","pressure":0.5},{"x":48.8,"y":22.9,"color":"black","pressure":0.5},{"x":53,"y":23,"color":"black","pressure":0.5},{"x":57.6,"y":22.9,"color":"black","pressure":0.5},{"x":61.6,"y":22.7,"color":"black","pressure":0.5},{"x":64.6,"y":22,"color":"black","pressure":0.5},{"x":67,"y":21.1,"color":"black","pressure":0.5},{"x":68.8,"y":19.9,"color":"black","pressure":0.5},{"x":69.8,"y":18.8,"color":"black","pressure":0.5},{"x":70.2,"y":17.7,"color":"black","pressure":0.5},{"x":68.8,"y":14.7,"color":"black","pressure":0.5}]},{"points":[{"x":56,"y":10.5,"color":"black","pressure":0.5},{"x":56,"y":10.5,"color":"black","pressure":0.5},{"x":56.2,"y":10.5,"color":"black","pressure":0.5},{"x":58,"y":10.5,"color":"black","pressure":0.5},{"x":61,"y":10.5,"color":"black","pressure":0.5},{"x":64,"y":10.5,"color":"black","pressure":0.5},{"x":66.6,"y":10.5,"color":"black","pressure":0.5},{"x":68.8,"y":10.5,"color":"black","pressure":0.5},{"x":70,"y":10.6,"color":"black","pressure":0.5},{"x":70.6,"y":10.7,"color":"black","pressure":0.5},{"x":70.8,"y":11.1,"color":"black","pressure":0.5},{"x":71,"y":11.7,"color":"black","pressure":0.5},{"x":71.2,"y":12.4,"color":"black","pressure":0.5},{"x":71.4,"y":13.1,"color":"black","pressure":0.5},{"x":71.6,"y":13.7,"color":"black","pressure":0.5},{"x":71.8,"y":14,"color":"black","pressure":0.5}]}]

signaturePad.fromData(points) // fails

signaturePad.fromData(points) throws an error due to division by zero error.

What is the expected behavior?
Sinature pad doesn't throw an error and draw on canvas.

Which versions of SignaturePad, and which browser / device are affected by this issue? Did this work in previous versions of SignaturePad?
Affected versions > 4.0.0

This PR proposes a fix
#785