fix(Scripts/Commands): Fix crash when using npc set origin faction wi… (azerothcore#20536)

Author: Nyeriah

src/server/scripts/Commands/cs_npc.cpp

@@ -483,6 +483,9 @@ class npc_commandscript : public CommandScript
         if (!player)
             return false;
 
+        if (!player->GetSelectedUnit())
+            return false;
+
         Creature* creature = player->GetSelectedUnit()->ToCreature();
 
         if (!creature)