In the editor UI, compositing process gets stuck while building the lighting in auto mode when the light mode is set to Stationary or Static. Baking process gets completed but editor progress bar is stuck. It is possible to reproduce it in a new scene. Sometimes UI can get stuck in different phases of lighting.

1) Open the scene `t1` or create a new scene with a lightmap static object
2) Switch the mode of light to `Stationary` or `Static`
3) Ensure that Auto mode is on
4) Observe the bug

Notes:
- Reproducible in 5.6.0b2, 5.6.0b3 and 5.6.0b5
- Not reproducible in 5.6.0a6 and 5.6.0b1
- Seems like it started to occur when light modes is merged to trunk, workaround is to use manual lighting