npc.php: add sanity check NPC is actually an NPC
npc.php: add sanity check NPC is actually an NPC

We want to be sure that we never modify a real player, so add a
sanity check just to be certain.

smrealms/smr,smrealms/smr,hemberger/smr,smrealms/smr,hemberger/smr,hemberger/smr,hemberger/smr