Unable to drop extension dblink

In the process of removing extensions not required on the database I was 
in the process of removing the dblink extension from the postgres database.

First attempt to drop the extension failed with 'ERROR: schema 
"ag_catalog" does not exist'.

Created the extension and then received the 'ERROR: table "ag_label" 
does not exist'.

In response I created the table with a dummy colum 'label'.

Dropping the extension resulted in "ERROR: index 
"pgsql-admin@lists.postgresql.org"'. So I created the index.

Next attempt resulted in 'ERROR:  column is not in index'.

Now I appear to be stuck in a loop with 'ERROR:  column is not in index' 
regardless of any attempt to remove these tables and the original 
extension.

Any assistance appreciated.

Regards

Matt.