Pencil: Polyline draw in Vector mode

[DIane-Kivi]

If you draw a polyline, then draw another, the first line vanishes until the second draw process is complete! This is disconcerting and makes multi line drawings difficult to draw. The problem only occurs with polyline draw function.

During the drawing process only the polyline being draw appears on screen ### Actual Results

All previous poly lines to be displayed ### Expected Results

Vector ### Video or Image Reference

draw more than 1 polyline on a frame

Steps to reproduce

System Information

0.6.5 + Pencil2D Version:

Windows 10 + Operating System:

8 GB RAM Size:

None + Graphics Tablet:

Work around use version 0.6.4 for poly line drawing operations

[CandyFace]

This should be fixed via the linked PR that is awaiting.