Hey fmpstudio,
We did totally misunderstand the question, and for that we apologize.
However, the troubleshooting we shared can be helpful for your Smart Album issue too.
Have you restarted your Mac yet? Does the same thing happen with no other apps open after the restart?
Is the keyword present in your keyword list? If not, that should provide a "nothing found" response, but not the Photos app closing.
Does the same thing happen when using safe mode? It may take longer to finish the start up, as safe mode does some system checks, and can sometimes resolve issues. You'll also see some differences in the display. This is expected with safe mode, and when you restart normally, they'll be gone. Test, restart normally and test again.
The latest macOS for Big Sur is 11.5.2. For Photos it is 6.0, so that is up to date.
Update macOS on Mac
Thank you!