Only check for safe mode on versions that have it, refs #6300

src/Composer/Util/Git.php

@@ -252,7 +252,7 @@ class Git
 
     public static function cleanEnv()
     {
-        if (ini_get('safe_mode') && false === strpos(ini_get('safe_mode_allowed_env_vars'), 'GIT_ASKPASS')) {
+        if (PHP_VERSION_ID < 50400 && ini_get('safe_mode') && false === strpos(ini_get('safe_mode_allowed_env_vars'), 'GIT_ASKPASS')) {
             throw new \RuntimeException('safe_mode is enabled and safe_mode_allowed_env_vars does not contain GIT_ASKPASS, can not set env var. You can disable safe_mode with "-dsafe_mode=0" when running composer');
         }