It's not that you don't have a [Gmail]/Trash folder on the server. It's that Gmail doesn't have folders to begin with, only labels, and it presents to the mail client the labels corresponding to standard IMAP folders (but not other labels) as if they were subfolders of a folder called [Gmail]. So you have this folder in Thunderbird because Gmail tells Thunderbird this folder exists on the IMAP server, even though it doesn't really exist as such in Gmail itself.

Now, this being a Trash folder that's causing you trouble, I'd suggest to just get rid of it and let Thunderbird recreate it again. Go to your profile folder in the filesystem, quit Thunderbird, then go to the ImapMail/[account folder]/[Gmail].sbd folder and remove the files Trash and Trash.msf from there.

Thanks David ... unfortunately the error still pops up. I deleted the Trash. Gmail/Junk and Junk folders and I still get the error when Thunderbird starts.

Really? Thunderbird keeps wanting and failing to compact a folder it created anew? Does that folder have messages? Does Thunderbird show in that folder the same messages that you may see with webmail?

I don't know what's going on. but this being an IMAP account, you could try deleting the account in Thunderbird (both info and data) and set it up again. Quit Thunderbird and make a backup copy of your profile folder first, just in case, but everything stored on the server should be back when Thunderbird synchronises with the server after setting up the account again.