fix(track): a tributary loads as a river of its first path keeping the second, a track of an unknown type is left out, where both made the simulator fall over as it loaded

On master neither got a segment: update_location() dereferenced the missing one of a track of an unknown type, and
a tributary went to Switch(0), which logged "Cannot switch normal track", with no segment under it either.

A tributary is now a river of its first path. Its second path is kept in m_paths, isn't drawn nor run on, and is
written back with the type "tributary". A track of an unknown type is logged and left out by the loader; as it is no
node, its text stays in the file when the editor saves the scenery.

simulation/simulationstateserializer.cpp

@@ -543,6 +543,12 @@ state_serializer::deserialize_node( cParser &Input, scene::scratch_data &Scratch
     else if( nodedata.type == "track" ) {
 
         auto *path { deserialize_path( Input, Scratchpad, nodedata ) };
+        if( path->eType == tt_Unknown ) {
+            // with no path made it can't be joined nor drawn, and nothing could run on it
+            ErrorLog( "Bad scenario: track \"" + path->name() + "\" of an unknown type defined in file \"" + Input.Name() + "\" (line " + std::to_string( inputline ) + ") left out" );
+            delete path;
+            return;
+        }
         // duplicates of named tracks are currently experimentally allowed
         if( false == simulation::Paths.insert( path ) ) {
             ErrorLog( "Bad scenario: duplicate track name \"" + path->name() + "\" defined in file \"" + Input.Name() + "\" (line " + std::to_string( inputline ) + ")" );

world/Track.cpp

@@ -427,11 +427,15 @@ void TTrack::Load(cParser *parser, glm::dvec3 const &pOrigin)
     }
     else if (str == "tributary")
     {
-        eType = tt_Tributary;
+        // dopływ: no path of it was ever made, the simulator falling over it as it loaded. a river of its first path now, the
+        // second one kept and written back
+        ErrorLog("Bad track: tributary \"" + m_name + "\" in file \"" + parser->Name() + "\" (line " + std::to_string(parser->Line()) + ") is drawn and run on as a river of its first path");
+        eType = tt_Normal;
         iCategoryFlag = 4;
+        m_tributary = true;
     }
     else
-        eType = tt_Unknown;
+        eType = tt_Unknown; // left out by the loader
     if (Global.iWriteLogEnabled & 4)
         WriteLog(str);
     parser->getTokens(4);
@@ -517,6 +521,11 @@ void TTrack::Load(cParser *parser, glm::dvec3 const &pOrigin)
             break;
         }
     }
+    if( m_tributary ) {
+        // the second path of a tributary, kept to be written back
+        m_paths.emplace_back();
+        m_paths.back().deserialize( *parser, pOrigin );
+    }
 
     init_segments( true );
 
@@ -681,6 +690,10 @@ void TTrack::Load(cParser *parser, glm::dvec3 const &pOrigin)
         m_name = m_name.substr(0, i - 1); // usunięcie z nazwy
     }
 
+    if( CurrentSegment() == nullptr ) {
+        // of an unknown type, no path of it is made
+        return;
+    }
     update_location();
     // sleeper transforms are baked later in create_geometry(), once the owning cell has
     // assigned this track its m_origin (otherwise the local-space matrices would be relative
@@ -2314,6 +2327,7 @@ TTrack::export_as_text_( std::ostream &Output ) const {
     // type
     Output << (
             eType == tt_Normal ? (
+                m_tributary ? "tributary" :
                 iCategoryFlag == 1 ? "normal" :
                 iCategoryFlag == 2 ? "road" :
                 iCategoryFlag == 4 ? "river" :

world/Track.h

@@ -187,6 +187,7 @@ public:
 
     std::vector<segment_data> m_paths; // source data for owned paths
     bool m_editorremoved { false };
+    bool m_tributary { false }; // loaded as a tributary: a river of its first path, the second one kept to be written back
     scene::basic_node *m_road { nullptr }; // road or road junction which generated this path. such path is one-way, and isn't saved nor edited on its own
     std::array<float, 3> m_routeweights { 0.f, 0.f, 0.f }; // odds of each route through a crossroads being picked by a driver, by the number of the route. all zero: even odds
 	int iterate_stamp = 0;