PHPCAS-53 Fix warning when destroying an unitialized session, patch from Yann Richard,Joachim Fritschi
PHPCAS-53 Fix warning when destroying an unitialized session, patch from Yann Richard,Joachim Fritschi

git-svn-id: 94f0db08461a0213b6c0921e79b985cd37b48048@20214 f5dbab47-78f9-eb45-b975-e544023573eb

yangchunyong/phpCAS,chand3040/phpCAS,neopeak/phpCAS,mickelfeng/phpCAS,snelg/phpCAS,rakesh-mohanta/phpCAS,fh/phpCAS,Jasig/phpCAS