Fix a typo with logic check, and valid results not shown

Re #26063

qt/scientific_interfaces/ISISReflectometry/GUI/Experiment/ExperimentPresenter.cpp

@@ -198,8 +198,10 @@ std::string ExperimentPresenter::transmissionStitchParamsFromView() {
   // If set, the params should be a list containing an odd number of double
   // values (as per the Params property of Rebin)
   auto maybeParamsList = parseList(stitchParams, parseDouble);
-  if (maybeParamsList.is_initialized() && maybeParamsList->size() % 2 == 0)
+  if (maybeParamsList.is_initialized() && maybeParamsList->size() % 2 != 0) {
+    m_view->showTransmissionStitchParamsValid();
     return stitchParams;
+  }
 
   m_view->showTransmissionStitchParamsInvalid();
   return std::string();