Cut hole/Edit object tool: two-vertex holes

[lpechacek]

Two-vertex holes are created by the Edit object tool.

1. Create an area object
2. Cut a triangular hole
3. Select Edit tool and delete one vertex of the triangular hole

Actual result:
There is infinitely thin two-vertex hole in the area.

Expected result:
The whole hole is removed as soon as it degrades to two vertices.