RunModel_Lag: extra `names` attribute on `OutputsModel$Qsim`

Following the modifications of #123 (closed), airGRiwrm has failed tests as described in in-wop/airGRiwrm#50 (closed)

When using Qupstream for initial states of the lag model, OutputsModel$Qsim has an attribute "names" with empty strings.

This attribute must be removed in any case.