How to reproduce:
1. Open the project attached by the user (SphericalWindZoneBug.zip)
2. Open the "SampleScene" Scene
3. Enable the "DirectionalWindZone" GameObject, play the Scene
4. Observe as the particles and tree move in the same direction
5. Disable the "DirectionalWindZone" GameObject, enable the "SphericalWindZone" GameObject
6. Observe as the particles are attracted to the SphericalWindZone, while the tree is repelled from it

Expected result: Particles and Trees should react the same way to Spherical Wind Zones
Actual result: Trees and Particles are affected oppositely by Spherical Wind Zones

Reproducible with: 5.6, 2017.1.0a1, 2017.1.4p2, 2017.2.3p1, 2017.4.6f1, 2018.1.7f1, 2018.2.0b11, 2018.3.0a3

Notes: Setting the "Main" values of the wind zones from 10 to -10 also helps to display the bug better.