kmswebrtcendpoint: Avoid illegal memory access releasing a NULL pointer
kmswebrtcendpoint: Avoid illegal memory access releasing a NULL pointer

Change-Id: I5456addd1222357ea50e38b42849d163b805369c

shelsonjava/kms-elements,TribeMedia/kms-elements,TribeMedia/kms-elements,shelsonjava/kms-elements,shelsonjava/kms-elements,TribeMedia/kms-elements