Stylesheet: Disable extendend @import statements provided by LESS

fixes #9687

library/Icinga/Web/LessCompiler.php

@@ -8,7 +8,6 @@ use RecursiveDirectoryIterator;
 use RecursiveIteratorIterator;
 use RegexIterator;
 use RecursiveRegexIterator;
-use Zend_Controller_Front;
 use Icinga\Application\Icinga;
 use lessc;
 
@@ -31,8 +30,6 @@ class LessCompiler
      */
     private $lessc;
 
-    private $baseUrl;
-
     private $source;
 
     /**
@@ -44,6 +41,17 @@ class LessCompiler
         $this->lessc = new lessc();
     }
 
+    /**
+     * Disable the extendend import functionality
+     *
+     * @return  $this
+     */
+    public function disableExtendedImport()
+    {
+        $this->lessc->importDisabled = true;
+        return $this;
+    }
+
     public function compress()
     {
         $this->lessc->setPreserveComments(false);

library/Icinga/Web/StyleSheet.php

@@ -99,6 +99,7 @@ class StyleSheet
         }
 
         $less = new LessCompiler();
+        $less->disableExtendedImport();
         foreach ($lessFiles as $file) {
             $less->addFile($file);
         }