fix a double-free bug, spotted by fendrin, and an issue with -e --load,

src/editor2/editor_main.cpp

@@ -51,6 +51,7 @@ EXIT_STATUS start(config& game_conf, CVideo& video, const std::string& filename
 			}
 		}
 		editor_controller editor(game_conf, video, mc.get());
+		mc.release();
 		if (!map_error.empty()) {
 			gui::message_dialog(editor.gui(), _("Error loading map"), map_error).show();
 		}

src/game.cpp

@@ -1128,6 +1128,7 @@ bool game_controller::goto_editor()
 			return false;
 		}
 	}
+	loaded_game_ = "";
 	return true;
 }
 #endif