NEW:tracking stl model files

jira:[STUDIO-5372]

Change-Id: Idb1275b07441f0cd06c24588d5f7c20f81f1556c

src/libslic3r/Format/STL.cpp

@@ -17,6 +17,8 @@ namespace Slic3r {
 bool load_stl(const char *path, Model *model, const char *object_name_in, ImportstlProgressFn stlFn)
 {
     TriangleMesh mesh;
+    std::string design_id;
+
     if (! mesh.ReadSTLFile(path, true, stlFn)) {
 //    die "Failed to open $file\n" if !-e $path;
         return false;
@@ -59,4 +61,4 @@ bool store_stl(const char *path, Model *model, bool binary)
     return store_stl(path, &mesh, binary);
 }
 
-}; // namespace Slic3r
+}; // namespace Slic3r