Fixed empty filename when trying to export a plate where no object is selected and no object is printable

src/slic3r/GUI/Plater.cpp

@@ -2518,6 +2518,10 @@ wxString Plater::priv::get_export_file(GUI::FileType file_type)
         if (output_file.empty())
             // Find the file name of the first printable object.
             output_file = this->model.propose_export_file_name_and_path();
+
+        if (output_file.empty() && !model.objects.empty())
+            // Find the file name of the first object.
+            output_file = this->model.objects[0]->get_export_filename();
     }
 
     wxString dlg_title;