Do not create a "mailto" hyperlink for empty email addresses.

git-svn-id: http://svn.code.sf.net/p/itop/code/trunk@927 a333f486-631f-4898-b8df-5754b55c2be0

core/attributedef.class.inc.php

@@ -1091,6 +1091,7 @@ class AttributeEmailAddress extends AttributeString
 
 	public function GetAsHTML($sValue)
 	{
+		if (empty($sValue)) return '';
 		return '<a class="mailto" href="mailto:'.$sValue.'">'.parent::GetAsHTML($sValue).'</a>';
 	}
 }