Reproduction steps:
1. Create and open a new project;
2. Create empty Game object;
3. Add the Hinge joint to it;
4. Disable the Game object;
5. Press "Edit Joint" button.

Expected results: Editor won't crash after trying to edit joint and/or will show an error message.
Actual results: Editor crash right after trying to edit Hinge joint.

Reproduced on: 2017.2.1p2, 2017.3.0p4, 2018.1.0b5, 2018.2.0a1.