Steps to repro:

1. Open attached project and 'test' scene;
2. Open Lighting Setting windows (Window>Lighting>Settings);
3. Click 'Generate Lighting' button;
4. Resize the Lighting tab by clicking and dragging its left edge to the rightmost side;
5. Observe the baking control buttons under the 'Debug Settings' section.

Expected result:
All baking control buttons are visible after resizing the Lighting tab. See attached expected.png screenshot.

Actual result:
'Cancel' button is shifted to the right and partially not visible. See attached actual.png screenshot.

Notes:
- Reproducible in 2018.1.0a7, 2017.3.0f2, 2017.2.1f1, 2017.1.2p4;
- Reproducible on Windows and macOS;
- Reproducible only for PLM apparently because of additional 'Force Stop' button appearing when it's set; not reproducible for Enlighten.