Handle unexpected os when loading yaml (#9790)

includes/common.php

@@ -1601,6 +1601,7 @@ function load_all_os($existing = false, $cached = true)
         }
 
         foreach ($os_list as $file) {
+            if (is_readable($file)) {
                 $tmp = Symfony\Component\Yaml\Yaml::parse(file_get_contents($file));
 
                 if (isset($config['os'][$tmp['os']])) {
@@ -1610,6 +1611,7 @@ function load_all_os($existing = false, $cached = true)
                 }
             }
         }
+    }
 }
 
 /**