Fix for NPE when monitoring data are pulled from the server which has metrics history set to off.
Fix for NPE when monitoring data are pulled from the server which has metrics history set to off.

git-svn-id: 4a0daf30c0bbd291b3bc5fe8f058bf11ee523347@2899 7d282ba1-3ae6-0310-8f9b-c9008a0864d2

nate-sentjens/tigase-xmpp-java,nate-sentjens/tigase-xmpp-java,cgvarela/tigase-server,Smartupz/tigase-server,Smartupz/tigase-server,f24-ag/tigase,Smartupz/tigase-server,fanout/tigase-server,nate-sentjens/tigase-xmpp-java,sourcebits-praveenkh/Tagase,amikey/tigase-server,wangningbo/tigase-server,fanout/tigase-server,cgvarela/tigase-server,nate-sentjens/tigase-xmpp-java,caiyingyuan/tigase71,wangningbo/tigase-server,wangningbo/tigase-server,cgvarela/tigase-server,pivotal-nathan-sentjens/tigase-xmpp-java,Smartupz/tigase-server,Smartupz/tigase-server,pivotal-nathan-sentjens/tigase-xmpp-java,nate-sentjens/tigase-xmpp-java,wangningbo/tigase-server,nate-sentjens/tigase-xmpp-java,sourcebits-praveenkh/Tagase,sourcebits-praveenkh/Tagase,cgvarela/tigase-server,caiyingyuan/tigase71,amikey/tigase-server,fanout/tigase-server,pivotal-nathan-sentjens/tigase-xmpp-java,amikey/tigase-server,caiyingyuan/tigase71,amikey/tigase-server,wangningbo/tigase-server,fanout/tigase-server,fanout/tigase-server,pivotal-nathan-sentjens/tigase-xmpp-java,sourcebits-praveenkh/Tagase,pivotal-nathan-sentjens/tigase-xmpp-java,caiyingyuan/tigase71,pivotal-nathan-sentjens/tigase-xmpp-java,f24-ag/tigase,fanout/tigase-server,f24-ag/tigase,amikey/tigase-server,cgvarela/tigase-server,wangningbo/tigase-server,Smartupz/tigase-server,caiyingyuan/tigase71,wangningbo/tigase-server,caiyingyuan/tigase71,amikey/tigase-server,cgvarela/tigase-server,f24-ag/tigase,f24-ag/tigase,sourcebits-praveenkh/Tagase,f24-ag/tigase,sourcebits-praveenkh/Tagase