Steps to reproduce:
1. Create a gameObject with a Light Component attached
2. In the inspector Window of that gameObject, add a Flare to the 'Flare' property in the Light Component
3. Add any Collider to the same gameObject and try turning it off/on

Expected: the flare is visible regardless of Collider's active status
Actual: the flare disappears when the Collider is turned on

Reproduced in: 2017.2.0b4, 2017.2.2p4, 2017.4.2f2, 2018.1.0f2, 2018.2.0b3
Not reproduced in: 2017.1.3p4, 2017.2.0b3

Note: works with any collider, works with 'point', 'spot' and 'area' Light Type (did not manage to get directional to function with the flare)