fix notice "Undefined offset: 2", add support Bing Optimized IE

"Notice: Undefined offset: 2" in Woothee\AgentCategory\Browser\Msie.php on line 17

MSIE11 (Bing Optimized) + Windows 7
Mozilla/5.0 (Windows NT 6.1; Trident/7.0; BOIE9;JAJP; rv:11.0) like Gecko