Plugins should not overwrite existing config props

program/include/rcube_config.php

@@ -132,12 +132,12 @@ class rcube_config
    * @param string Full path to the config file to be loaded
    * @return booelan True on success, false on failure
    */
-  public function load_from_file($fpath)
+  public function load_from_file($fpath, $merge = true)
   {
     if (is_file($fpath) && is_readable($fpath)) {
       include($fpath);
       if (is_array($rcmail_config)) {
-        $this->prop = array_merge($this->prop, $rcmail_config);
+        $this->prop = $merge ? array_merge($this->prop, $rcmail_config) : $this->prop + $rcmail_config;
         return true;
       }
     }

program/include/rcube_plugin.php

@@ -59,7 +59,7 @@ abstract class rcube_plugin
   {
     $fpath = $this->home.'/'.$fname;
     $rcmail = rcmail::get_instance();
-    if (!$rcmail->config->load_from_file($fpath)) {
+    if (!$rcmail->config->load_from_file($fpath, false)) {
       raise_error(array('code' => 527, 'type' => 'php', 'message' => "Failed to load config from $fpath"), true, false);
       return false;
     }