Check replist is not NULL inline before doing any processing.

The replist is often NULL, so it is worth checking for that case before making
the function call to perform the work on the list.

Pass buildbot scripts:
- PR build: https://buildbot.openinfosecfoundation.org/builders/ken-tilera/builds/23
- PR pcap: https://buildbot.openinfosecfoundation.org/builders/ken-tilera-pcap/builds/30