Don't allow saves with an invalid last generated RefNum to load

CHANGELOG.md

@@ -52,6 +52,7 @@
     Bug #7092: BSA archives from higher priority directories don't take priority
     Bug #7122: Teleportation to underwater should cancel active water walking effect
     Bug #7131: MyGUI log spam when post processing HUD is open
+    Bug #7134: Saves with an invalid last generated RefNum can be loaded
     Bug #7163: Myar Aranath: Wheat breaks the GUI
     Bug #7172: Current music playlist continues playing indefinitely if next playlist is empty
     Bug #7229: Error marker loading failure is not handled

apps/openmw/mwlua/worldview.cpp

@@ -81,7 +81,10 @@ namespace MWLua
     void WorldView::load(ESM::ESMReader& esm)
     {
         esm.getHNT(mSimulationTime, "LUAW");
-        MWBase::Environment::get().getWorldModel()->setLastGeneratedRefNum(esm.getFormId(true));
+        ESM::FormId lastGenerated = esm.getFormId(true);
+        if (lastGenerated.hasContentFile())
+            throw std::runtime_error("Last generated RefNum is invalid");
+        MWBase::Environment::get().getWorldModel()->setLastGeneratedRefNum(lastGenerated);
     }
 
     void WorldView::save(ESM::ESMWriter& esm) const