Fixing throttle mediator transformer

git-svn-id: https://svn.wso2.org/repos/wso2/trunk/tools@162050 a5903396-d722-0410-b921-86c7d4935375
Fixing potential NPE

git-svn-id: https://svn.wso2.org/repos/wso2/trunk/tools@162054 a5903396-d722-0410-b921-86c7d4935375