Fix PC editor thinking a file is loaded even when the load failed

osx/pcedit/pc.main.cpp

@@ -227,7 +227,7 @@ void handle_file_menu(int item_hit)
 			if(verify_restore_quit(true)){
 				file = nav_get_party();
 				if(!file.empty()) {
-					load_party(file);
+					if(load_party(file))
 						file_in_mem = file;
 				}
 				menu_activate();