fix(CreateInputsModel): remove negative flow for data gap in Qupstream

- this element was added in first place because Qupstream didn't accept `NAs` in airGR. It's not the case anymore.

Refs #57

R/CreateInputsModel.GRiwrm.R

@@ -99,7 +99,6 @@ CreateInputsModel.GRiwrm <- function(x, DatesR,
   })
 
   InputsModel <- CreateEmptyGRiwrmInputsModel(x)
-  Qobs[is.na(Qobs)] <- -99 # airGR::CreateInputsModel doesn't accept NA values
 
   for(id in getNodeRanking(x)) {
     message("CreateInputsModel.GRiwrm: Treating sub-basin ", id, "...")