Correct logic check for Windows compatibility related to sys_getload_…

…avg function

src/DOFileCache.php

@@ -119,7 +119,7 @@ public function get($key)
             return false;
         }
 
-        if (!function_exists('sys_getloadavg')) {
+        if (!function_exists('sys_getloadavg') && $this->config['unixLoadUpperThreshold'] !== -1) {
             throw new Exception('Your PHP installation does not support `sys_getloadavg` (Windows?). Please set `unixLoadUpperThreshold` to `-1` in your DOFileCache config.');
         }