Connection leave drawing artefact if mouse leaves browser window during connect operation

[icyield]

See for example https://freegroup.github.io/draw2d/index.html#/examples/port_semantic_group When connection a port if the mouse pointer is moved outside the browser and then returns a dashed line is left on the canvas after a connection is made. Seems browser independent as same issue in chrome macos and safari.

Also seems to lose some other state information, for example cannot delete shapes, ports become unattached, etc ...

https://freegroup.github.io/draw2d/index.html#/examples/buildin_commandstack

PS: Great work! Has the same issue in your brainbox simulator.

[icyield]

A quick fix is to add mouseleave to the mouseup detection in Canvas.js:170 this.html.bind("mouseup touchend mouseleave", function (event) {

This changes more than just the connection dragging of course.