[Bug]: Arb Tx Filter Out Of Index Error On Non Affiliated Swap Msgs

[NotJeremyLiu]

What happened?

• After upgrading to v20.3.0, it was noticed that cosmwasm contract calls would panic during the arb tx fee filtering process.
• This happened due to an index out of range error here:

  osmosis/x/txfees/keeper/txfee_filters/arb_tx.go

  Line 46 in 4c54425

  lastPoolInRoute := m.Routes[len(m.Routes)-1]

• It is the case that even when the msgExecuteContract.Msg is not the exact same as the AffiliateSwapMsg type, the error may be nil

  osmosis/x/txfees/keeper/txfee_filters/arb_tx.go

  Line 106 in 4c54425

  if err := json.Unmarshal(contractMessage, &affiliateSwapMsg); err != nil {

  , allowing the filtering process to later call:

  osmosis/x/txfees/keeper/txfee_filters/arb_tx.go

  Line 113 in 4c54425

  swapInDenom, isArb := isArbTxLooseSwapMsg(affiliateSwapMsg, swapInDenom)

Possible Solution:
Add a check that if the len(Routes) is zero after unmarshaling to return early.

Osmosis Version

20.3.0

How to reproduce?

No response

[NotJeremyLiu]

Resolved by #6906