Yes, I found that link you cited a day ago and tried it before seeing your post.
Found my file under ~/Library/Containers/com.apple.Safari/Data/Library/Preferences/com.apple.Safari.Extensions.plist.
Crashed Thread: 0 Dispatch queue: com.apple.main-thread
Exception Type: EXC_BAD_INSTRUCTION (SIGILL)
Exception Codes: 0x0000000000000001, 0x0000000000000000
Exception Note: EXC_CORPSE_NOTIFY
Termination Signal: Illegal instruction: 4
Termination Reason: Namespace SIGNAL, Code 0x4
Terminating Process: exc handler 
ERROR /Users/danielcarlock/Library/Safari/Databases/safari-extension_yoo.david.sessions-deub45nr9t_0/ is either unreadable or contains no databases.
What should I try next?