Enigma: Fix compatibility with assets_dir

CHANGELOG

@@ -10,6 +10,7 @@ CHANGELOG Roundcube Webmail
 - Fix folders list sorting on Windows - if php-intl is available (#5732)
 - Fix addressbook searching by gender (#5757)
 - Fix prevention from using % and * characters in folder name (#5762)
+- Enigma: Fix compatibility with assets_dir
 
 RELEASE 1.3-rc
 --------------

plugins/enigma/lib/enigma_ui.php

@@ -116,14 +116,12 @@ class enigma_ui
      */
     function add_css()
     {
-        if ($this->css_loaded)
+        if ($this->css_loaded) {
             return;
+        }
 
         $skin_path = $this->enigma->local_skin_path();
-        if (is_file($this->home . "/$skin_path/enigma.css")) {
         $this->enigma->include_stylesheet("$skin_path/enigma.css");
-        }
-
         $this->css_loaded = true;
     }