[Bug]: gov module LegacyProposals API is not working when empty proposal is submitted

[Hemanthghs]

Summary of Bug

Legacy Proposals API is not working if empty proposal is submitted.
If an empty proposal is submitted then Legacy Proposals API is not returning the previous proposals also.
First I have submitted a Software upgrade proposal and I tried to get the proposals with legacy API, then it has returned the proposal without any problem.
Immediately I have submitted a second proposal which is an empty proposal and tried to get the proposals, It is not returning the all proposals instead it is returning the following response.

{
    "code": 2,
    "message": "codespace sdk code 29: invalid type: can't convert a gov/v1 Proposal to gov/v1beta1 Proposal when amount of 
    proposal messages is more than one",
    "details": [ ]
}

Version

v0.46.x

Steps to Reproduce

1. First submit a non empty proposal (Example: "/cosmos.upgrade.v1beta1.MsgSoftwareUpgrade" )
2. Next submit an empty proposal as follows

    {
      "metadata": "ipfs://CID",
      "deposit": "1909stake"
    }

3. Now call the LegacyProposals API ( http://localhost:1317/cosmos/gov/v1beta1/proposals )

[julienrbrt]

This is behaving as expected, actually. The endpoint will not return correct data if it was skipping a proposal.
Hence, it simply fails: #14347 (comment)

[julienrbrt]

We could convert a proposal without message to a legacy text proposal, but I am not sure if that will render well, given metadata will just be dumped as it. What do you think @alexanderbez?