Fixed SegFault error

Program was segfaulting under certain conditions (i.e. debug build)
  because the memory wasn't being set to NULL. Made change to set memory
  to NULL in triangle and valgrind is happy.


Former-commit-id: 4f02db3304ceedfad2298301063666e9757b8d9c

include/igl/triangle/triangulate.cpp

@@ -193,6 +193,7 @@ IGL_INLINE void igl::triangle::triangulate(
   out.pointlist = NULL;
   out.trianglelist = NULL;
   out.segmentlist = NULL;
+  out.segmentmarkerlist = NULL;
 	out.pointmarkerlist = NULL;
 
   // Call triangle