Script/Commands: Fix crash in .pet create command if Unit::CreateTamedPetFrom returns nullptr (#31218)

Author: HelloKitty

src/server/scripts/Commands/cs_pet.cpp

@@ -95,6 +95,12 @@ class pet_commandscript : public CommandScript
 
         // Everything looks OK, create new pet
         Pet* pet = player->CreateTamedPetFrom(creatureTarget);
+        if (!pet)
+        {
+            handler->PSendSysMessage("CreateTamedPetFrom returned null.");
+            handler->SetSentErrorMessage(true);
+            return false;
+        }
 
         // "kill" original creature
         creatureTarget->DespawnOrUnsummon();