Web\UrlParams: allow to merge single value

library/Icinga/Web/UrlParams.php

@@ -181,6 +181,9 @@ class UrlParams
                 $this->set($k, $v);
             }
         } else {
+            if (! is_array($values)) {
+                $values = array($values);
+            }
             foreach ($values as $value) {
                 $this->set($param, $value);
             }