This looks like a corrupted data base for the iMovie Library. Notice that the event has no event icon and looks like a clip. What you can try is close iMovie and go to the Library in the finder, probably in your movies folder on your boot drive unless you moved it. Save/duplicate it to your desktop as a precaution. Then right click on the original and select show package contents. Find and delete the CurrentVersion.flexolibrary file. Close the Library, reboot and then reopen iMovie. It should rebuild that file and you should be okay.