Fixed loading of configuration files after reverting to a snapshot

storing the old configuration format.

xs/src/slic3r/GUI/PresetBundle.cpp

@@ -210,6 +210,10 @@ std::string PresetBundle::load_system_presets()
                 errors_cummulative += "\n";
             }
         }
+	if (first) {
+		// No config bundle loaded, reset.
+		this->reset(false);
+	}
     return errors_cummulative;
 }