How to reproduce:
1. Create new project
2. In Project window, create a timeline by right-clicking the window -> Create -> Timeline
3. Double-click on the created timeline
4. Make Timeline window active by clicking anywhere in the Timeline window
5. Press "Home" key and observe Console window

Expected result: no errors appear
Actual result: each time "Home" key is pressed the NullReferenceException is thrown (after each "Home" button press, the "End" button throws NullReferenceException once)

Reproducible with: 2018.1.0b11, 2018.1.0f2
Not reproducible with: 2017.1.0b1, 2017.1.3p4, 2017.2.3f1, 2017.4.2f2, 2018.1.0b10, 2018.2.0b3
Could not test with: 2017.1.0a1, 2017.1.0a6 because the feature was not yet implemented

Workaround: enter and exit Play mode

Fixed in: 2018.2.0a1 version