Setting strokeUniform:true breaks polygon points editing when the polygon is scaled

[graphics-et-al]

Version

5.0.0

Test Case

http://jsfiddle.net/wilheim/q7brhmcn/1/

Information about environment

Browser and Svelte

Steps To Reproduce

1. In the points editing example at http://fabricjs.com/custom-controls-polygon, set the polygon's strokeUniform property to true
2. Hit 'Toggle editing polygon' button
3. Move a control point

Expected Behavior

Only the control point moves

Actual Behavior

The whole polygon moves in unexpected ways

There's an inelegant workaround available by toggling the strokeUniform property when starting and stopping editing, but it's aesthetically terrible.

I suspect it has to do with some internal line weight not updating when scaled. The editing polygon works as expected when the polygon is not scaled.

[ShaMan123]

duplicate #7605
check out #7639