Empty Signal Emitter added on closing "Select Signal Emitter" window.

Steps to repro:
1. Open the attached project.
2. Hierarchy > Select Cube.
3. Windows > Sequencing > Timeline.
4. Cube Animator > Right Click > Add Signal Emitter from Signal Asset.
5. Close "Select Signal Emitter" window.

Actual Result:
Empty Signal Emitter added on closing "Select Signal Emitter" window.

Expected Result:
Empty Signal Emitter should not be added on closing "Select Signal Emitter" window.

Reproducible in:
2020.2.0a17, 2020.1.0b15, 2019.4.3f1, 2019.3.0f1 2019.30a1 with Package Version 1.5.0-preview.2, 1.4.0, 1.3.0, 1.2.15, 1.2.6.

Working fine in:
2019.2.1f1.

Environment:
Occurring on Windows 10 & Mac 10.15.