Reproduction Steps:
1. Import attached project.
2. Drag Cube from Assets into Scene View.
3. Cancel drag (for example with the Escape key).
4. Observe scene.

Expected result: Cube is removed from Scene View.
Actual result: Cube remains in Scene View and is not selectable. (GIF attached)

Note: After drag is cancelled, the cancelled GameObject will appear for every other Game Object that is dragged into the scene. If placed, the cancelled GameObject will appear in the Hierarchy. (GIF attached)

Reproducible with: 2017.1.0b1
Not reproducible with: 5.5.3f1, 5.6.0f3, 2017.1.0a3
Regression introduced in: 2017.1.0a4