Abort due to constraint violation UNIQUE constraint failed: onlineannounce.userid

[ghost]

I'm trying to set /greet but it returns to Command failed, check logs for more details.
The log said:

Command: ERROR: Mono.Data.Sqlite.SqliteException (0x80004005): Abort due to constraint violation
UNIQUE constraint failed: onlineannounce.userid
  at Mono.Data.Sqlite.SQLite3.Reset (Mono.Data.Sqlite.SqliteStatement stmt) [0x00096] in <2f714ef98a8f4e73b149f84ee80555a1>:0 
  at Mono.Data.Sqlite.SQLite3.Step (Mono.Data.Sqlite.SqliteStatement stmt) [0x00046] in <2f714ef98a8f4e73b149f84ee80555a1>:0 
  at Mono.Data.Sqlite.SqliteDataReader.NextResult () [0x00129] in <2f714ef98a8f4e73b149f84ee80555a1>:0 
  at Mono.Data.Sqlite.SqliteDataReader..ctor (Mono.Data.Sqlite.SqliteCommand cmd, System.Data.CommandBehavior behave) [0x00051] in <2f714ef98a8f4e73b149f84ee80555a1>:0 
  at (wrapper remoting-invoke-with-check) Mono.Data.Sqlite.SqliteDataReader:.ctor (Mono.Data.Sqlite.SqliteCommand,System.Data.CommandBehavior)
  at Mono.Data.Sqlite.SqliteCommand.ExecuteReader (System.Data.CommandBehavior behavior) [0x00006] in <2f714ef98a8f4e73b149f84ee80555a1>:0 
  at Mono.Data.Sqlite.SqliteCommand.ExecuteNonQuery () [0x00000] in <2f714ef98a8f4e73b149f84ee80555a1>:0 
  at TShockAPI.DB.DbExt.Query (System.Data.IDbConnection olddb, System.String query, System.Object[] args) [0x00043] in <ee5ce75026b74995a03fdbd3cc824395>:0 
  at OnlineAnnounceV2.DB.AddAnnouncement (OnlineAnnounceV2.OAInfo info) [0x00023] in <4c1bf48fa2134115854c4314aa64a0c8>:0 
  at OnlineAnnounceV2.OAMain.OACommand (TShockAPI.CommandArgs args) [0x0012d] in <4c1bf48fa2134115854c4314aa64a0c8>:0 
  at TShockAPI.Command.Run (System.String msg, System.Boolean silent, TShockAPI.TSPlayer ply, System.Collections.Generic.List`1[T] parms) [0x0001c] in <ee5ce75026b74995a03fdbd3cc824395>:0 

Yes I'm running this on my Linux server, Ubuntu 18.04 bionic 64-bit.
Is there anything I can do to fix this?