Playback mode doesn't toggle on pressing spacebar key in Timeline window

Steps to reproduce:

1) Import attached package > Open "MultipleClips" scene.
2) Select the cube gameObject in hierarchy and keep the Timeline window open.
3) Play the clip in Timeline window and press spacebar to toggle playback mode.

Expected result: Pressing spacebar should toggle the playback mode and not give a shortcut conflict warning.

Actual result: Pressing spacebar gives a shortcut conflict and playback mode doesn't toggle and this warning is printed in the console:
"Shortcut conflict detected for key binding Space.
Please resolve the conflict by rebinding one or more of the following shortcuts:
Window/Maximize View (Space)
Timeline/Play (Space)

UnityEditor.EditorApplication:Internal_CallGlobalEventHandler()"

Works fine on: 2018.2.0a6, 2018.2.0a1, 2018.1.0b13
Reproducible on : 2018.2.0b1, 2018.2.0a7

Environment: Occurs on Mac 10.13 and 10.12. Works fine on windows.