Corrected dispatchCallback not defined bug in firefox
Corrected dispatchCallback not defined bug in firefox

Change-Id: I2e64fcf2e41b0714f3a09a53b36639335cb64f04

shelsonjava/kurento-jsonrpc-js,Kurento/kurento-jsonrpc-js,KurentoLegacy/kws-rpc-builder,shelsonjava/kurento-jsonrpc-js,Kurento/kurento-jsonrpc-js,Kurento/kurento-jsonrpc-js