Quickly using alt-tab with a blueprint in a new window causes the event graph to capture input of the alt key

Quickly using alt-tab with a blueprint in a new window causes the event graph to capture input of the alt key. This issue does not occur when the blueprint is a tab of the main UE4 editor window. The issue does not occur if thew alt+tab key is held down for a period of time. This issue is not a regression.

Versions Tested: Issue occurs in all versions tested
4.17.2 - CL: 3658906
4.18.0 - CL: 3709383
4.19.0 - CL: 3650786

1. Create a new project (no template or starter content needed)
2. Open the Skysphere Blueprint and navigate to its event graph
3. quickly press the alt+tab and then immediately let go (the window does not need to change, please see attached gif for visual explanation)
4. Right click with the mouse and drag the mouse around
   Result: The mouse is now zooming in and out even though the alt key is not being pressed
   Expected result: The mouse lets you pan around the event graph