Possible bug when clicking on empty space will having target in event

[nodegin]

Here's a piece of my code

This is how I produce it, the white crosshair is my cursor

Normally if I click on empty space the opt.target should be undefined

However sometimes I clicked on down empty space

the opt.target returns a line that shouldn't appears in that position

and the line stroke changed to green

[asturur]

You should replicate with a simple jsfiddle without too much custom code.
then if it is in coffe script i cannot help.