Added trim() to function baseversion()

/api/theme/cart.php triggers a PHP-notice `PHP NOTICE: Undefined offset: 0 [Modules.php, line 403] ShoppErrors->php, ModuleFile->baseversion, ModuleFile->valid, ModuleFile->__construct, ModuleLoader->installed, ShoppAPIModules->__construct, Shopp->init, call_user_func_array, do_action, require_once, require_once, require_once [Modules.php, line 403]`

This seems due to spaces.