Hi!
Well, the issue reported in the error message originates from the SSH SFTP Updater Support plugin. I have found similar issue reported on their plugin support forums, but I need to dig into this deeper to make sure it is resolved correctly.
Until then, can you please try:
1. de-activating the SSH SFTP Updater
2. then activate the search plugin
3. then activating the other plugin again
That should very likely bypass the issue for now.