Canvas Bug in GH 0.6.0019

Hi David,

I have found a bug in this version that was also present in at least 0.6.0017.

When I click the mouse to draw a line on the canvas, and don't actually move before releasing the mouse button an error is thrown up. i.e just a single click

EH_Canvas.Canvas_MouseUp() D:\dev\rhino\labs\Grasshopper\EH_Canvas.vb (Line: 1238)

See attached file for event log.