gpui: Do not emit MouseUpEvent when exiting drag & drop (#9273)

Fixes #9198

Release Notes:

- Fixed a bug where empty panes could be created during drag & drop.
427d66990cPiotr Osiewicz committed on 3/13/2024, 10:37:34 AM· committed by GitHubparentac4bbb6
1 file changedLine totals unavailable