Cloning repo from github within Xcode leaves dialog box un-closeable

I am able to use Xcode to clone a repo from github. I go to the repo, example: https://github.com/weitieda/cs193p-2020-swiftui, I click on the Code download button, I copy the repo's URL, I go back to Xcode and click on Source Control in the main menu, and click Clone, and paste the copied URL into the dialog box. The download completes, I see the project in the Finder, but the Xcode clone dialog box does not close and cannot be closed. The dialog box has a "Cancel" button, but clicking on it simply plays a "tock" sound but it doesn't close the dialog box. Because the dialog box is modal, I can't even quit Xcode normally. The only way I know to close the dialog box is to Force-Quit Xcode using Option-Command-ESC. Anyone else experience this? How to solve this?