Steps to reproduce:
1. Create new project
2. Add particle system to scene (Create -> Effects -> Particle System)
3. In particle system's shape module set one axis scale to 0
4. In Scene window move Shapes vertex

Expected results: Vertex can be moved to the desired position
Actual results: Vertex disappears from scene window, Radius or Radius thickness value is set to NaN in particle system's shape module. If Radius thickness value is set to NaN "Invalid AABB a" exception is thrown.

Reproduced with: 2018.2.0a6, 2018.1.0b13, 2017.3.2f1, 2017.2.2p2, 2017.1.3p2

Note: Scale option for shape was introduced in 2017.1