fix: propagate Disconnect error from Executor.Close

Author: retran

mdl/executor/executor.go

@@ -323,15 +323,16 @@ func (e *Executor) IsConnected() bool {
 
 // Close closes the connection to the project and all SQL connections.
 func (e *Executor) Close() error {
+	var closeErr error
 	if e.backend != nil && e.backend.IsConnected() {
-		e.backend.Disconnect()
+		closeErr = e.backend.Disconnect()
 		e.backend = nil
 	}
 	if e.sqlMgr != nil {
 		e.sqlMgr.CloseAll()
 		e.sqlMgr = nil
 	}
-	return nil
+	return closeErr
 }
 
 // ----------------------------------------------------------------------------