Fix a bug for NpcStats::mUsedIds in savegames, and added a compile-time guard to prevent similar errors in the future.

components/esm/esmwriter.hpp

@@ -74,6 +74,18 @@ class ESMWriter
             endRecord(name);
         }
 
+private:
+        // Prevent using writeHNT with strings. This already happened by accident and results in
+        // state being discarded without any error on writing or reading it. :(
+        // writeHNString and friends must be used instead.
+        void writeHNT(const std::string &name, std::string data)
+        {
+        }
+        void writeT(const std::string& data)
+        {
+        }
+public:
+
         template<typename T>
         void writeHNT(const std::string& name, const T& data, int size)
         {

components/esm/npcstats.cpp

@@ -140,7 +140,7 @@ void ESM::NpcStats::save (ESMWriter &esm) const
 
     for (std::vector<std::string>::const_iterator iter (mUsedIds.begin()); iter!=mUsedIds.end();
         ++iter)
-        esm.writeHNT ("USED", *iter);
+        esm.writeHNString ("USED", *iter);
 
     if (mTimeToStartDrowning)
         esm.writeHNT ("DRTI", mTimeToStartDrowning);