Steps to reproduce:
1. Create a new project
2. Download and start importing any asset from the asset store
3. When a popup window to select which assets to import appears, click "Import"

Expected results: the import process starts
Actual results: import process doesn't start, editor window is not in focus. Pressing anywhere on the editor starts the import process.

Reproduced on: 2017.1.2f1, 2017.2.0f3, 2017.3.0f1, 2017.3.0p2

Note: Does not reproduce when importing a package from a local source