[simulator] fix crash on addTrain() when too long

Author: gfgit

shared/src/traintastic/simulator/simulator.cpp

@@ -2823,8 +2823,6 @@ bool Simulator::addTrain(const std::string_view& name, DecoderProtocol proto, ui
 
       train->length += item.vehicle->length + (empty ? 0.0f : data.trainCouplingLength);
       empty = false;
-
-      train->vehicles.push_back(item);
     }
 
     if(empty)
@@ -2981,6 +2979,15 @@ bool Simulator::addTrain(const std::string_view& name, DecoderProtocol proto, ui
       }
     };
 
+    // Add wagons to train only when sure train will be added
+    for(const auto& item : vehicles)
+    {
+      if(!item.vehicle || item.vehicle->activeTrain)
+        continue;
+
+      train->vehicles.push_back(item);
+    }
+
     // Place wagons in segments
     bool first = true;
     for(auto& item : train->vehicles | std::views::reverse)