multimedia/kodi: unbreak with clang 4.0

RssReader.cpp:269:19: error: ordered comparison between pointer and zero ('TiXmlElement *' and 'int')

while (itemNode > 0)
       ~~~~~~~~ ^ ~

RssReader.cpp:273:22: error: ordered comparison between pointer and zero ('TiXmlNode *' and 'int')

while (childNode > 0)
       ~~~~~~~~~ ^ ~

PR: 216075
Submitted by: tcberner
Approved by: maintainer timeout (2 weeks)