fix saveTri

Geo/MElement.cpp

@@ -624,7 +624,7 @@ void MElement::writeMSH(FILE *fp, double version, bool binary, int num,
   int par = (parentNum) ? 1 : 0;
   int dom = (dom1Num) ? 2 : 0;
   bool poly = (type == MSH_POLYG_ || type == MSH_POLYH_ || type == MSH_POLYG_B);
-  bool polyb  = (type == MSH_LIN_B );
+  bool polyl  = (type == MSH_LIN_B || type == MSH_LIN_C);
 
   // if poly loop over children
   if(CTX::instance()->mesh.saveTri && poly){
@@ -634,9 +634,10 @@ void MElement::writeMSH(FILE *fp, double version, bool binary, int num,
     }
     return;
   }
-  else if (CTX::instance()->mesh.saveTri && polyb){
-    MLine *l = (MLine*)this;
+  else if(CTX::instance()->mesh.saveTri && polyl){
+    MLine *l = new MLine(getVertex(0), getVertex(1));
     l->writeMSH(fp, version, binary, num, elementary, physical, 0, 0, 0, ghosts);
+    delete l;
     return;
   }