QPIDMSG: Additional NULL checks for QPID payload.
QPIDMSG: Additional NULL checks for QPID payload.

Adding further NULL checks to QPID payload code to resolve issues
flagged by unit tests.

Signed-off-by: Damian Maguire <21930bd10afdadbc1f53edcd2634e8f66a5e6d7a@nyx.com>

dmaguire/OpenMAMA,dpauls/OpenMAMA,MattMulhern/OpenMamaCassandra,dmagOM/OpenMAMA-dynamic,dpauls/OpenMAMA,cloudsmith-io/openmama,MattMulhern/OpenMAMA,kuangtu/OpenMAMA,fquinner/OpenMAMA,dpauls/OpenMAMA,fquinner/OpenMAMA,cloudsmith-io/openmama,fquinner/OpenMAMA,vulcanft/openmama,MattMulhern/OpenMAMA,dmagOM/OpenMAMA-dynamic,MattMulhern/OpenMAMA,cloudsmith-io/openmama,philippreston/OpenMAMA,jacobraj/MAMA,fquinner/OpenMAMA,philippreston/OpenMAMA,MattMulhern/OpenMAMA,fquinner/OpenMAMA,kuangtu/OpenMAMA,jacobraj/MAMA,vulcanft/openmama,dmaguire/OpenMAMA,kuangtu/OpenMAMA,dpauls/OpenMAMA,MattMulhern/OpenMamaCassandra,vulcanft/openmama,kuangtu/OpenMAMA,jacobraj/MAMA,vulcanft/openmama,MattMulhern/OpenMamaCassandra,dmagOM/OpenMAMA-dynamic,jacobraj/MAMA,dmagOM/OpenMAMA-dynamic,kuangtu/OpenMAMA,dmaguire/OpenMAMA,jacobraj/MAMA,philippreston/OpenMAMA,philippreston/OpenMAMA,vulcanft/openmama,dmaguire/OpenMAMA,cloudsmith-io/openmama,MattMulhern/OpenMamaCassandra,cloudsmith-io/openmama,cloudsmith-io/openmama,jacobraj/MAMA,philippreston/OpenMAMA,MattMulhern/OpenMAMA,dmagOM/OpenMAMA-dynamic,dpauls/OpenMAMA,vulcanft/openmama,dmaguire/OpenMAMA,MattMulhern/OpenMAMA,cloudsmith-io/openmama,dpauls/OpenMAMA,dmagOM/OpenMAMA-dynamic,philippreston/OpenMAMA,MattMulhern/OpenMAMA,fquinner/OpenMAMA,kuangtu/OpenMAMA,dpauls/OpenMAMA,dmaguire/OpenMAMA,dmaguire/OpenMAMA,MattMulhern/OpenMamaCassandra,MattMulhern/OpenMamaCassandra,fquinner/OpenMAMA,vulcanft/openmama,philippreston/OpenMAMA,kuangtu/OpenMAMA