Closing Appcenter during download breaks installing anything

When I'm downloading an app and forget about it, then close Appcenter and reopen it, I'm not able to redownload that app or any other app as there was a broken install. I can't even install something off of Terminal either due to the broken install.

Proposed solutions:

- Install apps in the background when closing Appcenter like how music still plays when closing Music.

- Give a warning that you're about to close Appcenter in the middle of a download.

- Pause the download so you can resume it after closing Appcenter(might go with number 2)