Photos in Catalina quits when I am asked to locate original image
Photos worked fine on an external disk that I replaced, so I moved my folder with all my photos (image files) back to my user directory and put the folder with all my photos (mostly in subfolders) and the Photos Library into my Pictures folder. Photos opens ok and all my albums are there, but when I click on a picture, Photos asks me to locate original image: when I do this, Photos unexpectantly quits. When I reopen Photos, the link to the particular image is now set, but same problem with any other image. I selected the correct Photos Library when opening by holding option key down. I also repaired Photos Library several times using option/command when opening. Zapping pram or resetting macmini by shutting down and disconnected power for 5 min. didn't help either. I assume there must be a corrupted preference but not sure where it is. I don't want to lose all the albums I organized in Photos (previously iPhotos a few years ago).
I also noticed a small file called "Photos Library.photoslibrary" (<1 KB) in my Pictures folder and not sure what it is. There are no other files on mac with name Photos Library
Using Macmini8,1 with 32 GB of RAM
Advice appreciated, THANKS
Mac mini 2018 or later