From 1d06d4e3c43e08bc4be0155296b6a40bc5044d7b Mon Sep 17 00:00:00 2001
From: Markus Frosch <markus.frosch@icinga.com>
Date: Thu, 17 Aug 2017 13:20:51 +0200
Subject: [PATCH] Form/Element/Number: The field should be valid when empty

---
 library/Icinga/Web/Form/Element/Number.php | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/library/Icinga/Web/Form/Element/Number.php b/library/Icinga/Web/Form/Element/Number.php
index b8f532c6f..212c0ed1d 100644
--- a/library/Icinga/Web/Form/Element/Number.php
+++ b/library/Icinga/Web/Form/Element/Number.php
@@ -134,7 +134,7 @@ class Number extends FormElement
     {
         $this->setValue($value);
         $value = $this->getValue();
-        if ($value !== '' && ! is_numeric($value)) {
+        if ($value !== null && $value !== '' && ! is_numeric($value)) {
             $this->addError(sprintf(t('\'%s\' is not a valid number'), $value));
             return false;
         }