Use null coalescing operator in currentProcessAuth

Before: currentProcessAuth() did $this->_args['authentication'] !== 'none', which assumes the key exists.

After: ($this->_args['authentication'] ?? null) !== 'none'.

Why: During logout, concurrent AJAX, or requests where _args was not fully set, PHP logged Undefined array key "authentication". This is a small hardening change; it does not change normal behavior when authentication is 'none', null, or unset (all treated as “auth not required for this process”). It mainly stops noise when apps call registry methods during/after session teardown.

Author: TDannhauer

lib/Horde/Registry.php

@@ -2330,7 +2330,7 @@ public function isAuthenticated(array $opts = [])
      */
     public function currentProcessAuth()
     {
-        return ($this->_args['authentication'] !== 'none');
+        return (($this->_args['authentication'] ?? null) !== 'none');
     }
 
     /**