Fix adding labels from plugins

program/include/rcube_json_output.php

@@ -130,8 +130,11 @@ class rcube_json_output
      */
     public function add_label()
     {
-        $arg_list = func_get_args();
-        foreach ($arg_list as $i => $name) {
+        $args = func_get_args();
+        if (count($args) == 1 && is_array($args[0]))
+            $args = $args[0];
+        
+        foreach ($args as $name) {
             $this->texts[$name] = rcube_label($name);
         }
     }