wormchain: tokenbridge: Don't allow self-registration

Don't allow registering an emitter for wormhole chain on wormhole chain.

wormhole_chain/x/tokenbridge/keeper/msg_server_execute_governance_vaa.go

@@ -84,6 +84,10 @@ func (k msgServer) ExecuteGovernanceVAA(goCtx context.Context, msg *types.MsgExe
 		chainId := binary.BigEndian.Uint16(payload[:2])
 		bridgeEmitter := payload[2:34]
 
+		if chainId == uint16(wormholeConfig.ChainId) {
+			return nil, types.ErrRegisterWormholeChain
+		}
+
 		if _, found := k.GetChainRegistration(ctx, uint32(chainId)); found {
 			return nil, types.ErrChainAlreadyRegistered
 		}

wormhole_chain/x/tokenbridge/types/errors.go

@@ -38,4 +38,5 @@ var (
 	ErrAmountTooHigh                  = sdkerrors.Register(ModuleName, 1133, "the amount would exceed the bridges capacity of u64")
 	ErrAssetMetaRollback              = sdkerrors.Register(ModuleName, 1134, "asset meta must have a higher sequence than the last update")
 	ErrNegativeFee                    = sdkerrors.Register(ModuleName, 1135, "fee cannot be negative")
+	ErrRegisterWormholeChain          = sdkerrors.Register(ModuleName, 1136, "cannot register an emitter for wormhole-chain on wormhole-chain")
 )