Fixed serializing with empty namespace ("")
Serializing dataContract with empty namespace on serviceContract with empty namespace ended with an exception (on property IDictionary<string,object> where value was an array of entities):
Exception The Namespace cannot be empty.   at System.Xml.XmlTextWriter.LookupPrefix (System.String ns) [0x00016] in /home/xxx/_projekt/monosrc/mono/mcs/class/System.XML/System.Xml/XmlTextWriter2.cs:402
  at System.Xml.DefaultXmlWriter.LookupPrefix (System.String ns) [0x00011] in /home/xxx/_projekt/monosrc/mono/mcs/class/System.XML/System.Xml/DefaultXmlWriter.cs:60