Core/Misc: Fix static analysis issues

Fix some static analysis issues reported by Coverity

src/server/game/Handlers/PetitionsHandler.cpp

@@ -177,7 +177,9 @@ void WorldSession::HandlePetitionShowSignatures(WorldPackets::Petition::Petition
         signature.Choice = 0;
         signaturesPacket.Signatures.push_back(signature);
 
-        result->NextRow();
+        // Checking the return value just to be double safe
+        if (!result->NextRow())
+            break;
     }
 
     SendPacket(signaturesPacket.Write());
@@ -447,7 +449,9 @@ void WorldSession::HandleOfferPetition(WorldPackets::Petition::OfferPetition& pa
         signature.Choice = 0;
         signaturesPacket.Signatures.push_back(signature);
 
-        result->NextRow();
+        // Checking the return value just to be double safe
+        if (!result->NextRow())
+            break;
     }
 
     player->GetSession()->SendPacket(signaturesPacket.Write());
@@ -551,7 +555,10 @@ void WorldSession::HandleTurnInPetition(WorldPackets::Petition::TurnInPetition&
     {
         Field* fields = result->Fetch();
         guild->AddMember(ObjectGuid::Create<HighGuid::Player>(fields[0].GetUInt64()));
-        result->NextRow();
+
+        // Checking the return value just to be double safe
+        if (!result->NextRow())
+            break;
     }
 
     SQLTransaction trans = CharacterDatabase.BeginTransaction();

src/server/game/Server/Packets/NPCPackets.h

@@ -85,8 +85,8 @@ namespace WorldPackets
             void Read() override;
 
             ObjectGuid GossipUnit;
-            int32 GossipIndex;
-            int32 GossipID;
+            int32 GossipIndex = 0;
+            int32 GossipID = 0;
             std::string PromotionCode;
         };
 

src/server/game/Server/Packets/SpellPackets.h

@@ -226,8 +226,8 @@ namespace WorldPackets
 
             void Read() override;
 
-            uint8 PackSlot;
-            uint8 Slot;
+            uint8 PackSlot = 0;
+            uint8 Slot = 0;
             ObjectGuid CastItem;
             SpellCastRequest Cast;
         };

src/server/game/Spells/SpellHistory.cpp

@@ -640,7 +640,7 @@ void SpellHistory::LockSpellSchool(SpellSchoolMask schoolMask, uint32 lockoutTim
     else if (Pet* petOwner = _owner->ToPet())
     {
         for (auto const& p : petOwner->m_spells)
-            if (p.second.state != PLAYERSPELL_REMOVED)
+            if (p.second.state != PETSPELL_REMOVED)
                 knownSpells.insert(p.first);
     }
     else