Fix explorer selection state when drag ends

[initialshl]

Fixes #2367

When a file is dragged onto tree view from desktop and escape key is pressed, the dragend event does not fire.

This fix relies on the property that such an event has a position of (0 , 0).

[mention-bot]

@initialshl, thanks for your PR! By analyzing the history of the files in this pull request, we identified @egamma and @jrieken to be potential reviewers.

[msftclas]

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[msftclas]

Hi @initialshl, I'm your friendly neighborhood Microsoft Pull Request Bot (You can call me MSBOT). Thanks for your contribution!
You've already signed the contribution license agreement. Thanks!

The agreement was validated by Microsoft and real humans are currently evaluating your PR.

TTYL, MSBOT;

[joaomoreno]

Looking great, thanks!