Bug: Draw "Done" button incorrectly enabled

[dannyleech]

"Done" button enabled with only two vertices after map movement on touch devices

Description:
On touch devices, after placing a second vertex and then moving the map, the "Done" button becomes enabled. It should only be enabled when at least three vertices are present.

Steps to Reproduce:

1. Open the map drawing tool on a touch device
2. Place the first vertex
3. Place a second vertex
4. Move/pan the map
5. Observe the "Done" button becomes enabled