fix: getMsgInfo returns an ErrNotFound when there are no rows

[virajbhartiya]

Related Issues

Closes #12674

Proposed Changes

GetMsgInfo returns an ErrNotFound when there are no rows.

Checklist

• Commits have a clear commit message.
• PR title conforms with contribution conventions
• Update CHANGELOG.md or signal that this change does not need it per contribution conventions
• New features have usage guidelines and / or documentation updates in
  • Lotus Documentation
  • Discussion Tutorials
• Tests exist for new functionality or change in behavior
• CI is green

[github-actions]

Please update the PR title to match https://github.com/filecoin-project/lotus/blob/master/CONTRIBUTING.md#pr-title-conventions

PR title now matches the required format.

[virajbhartiya]

@rvagg I have done a string comparison to check for the error and return ErrNotFound Please let me know if that's the way to go about it or there's a better way for this

[virajbhartiya]

@rvagg I just ran TestEthBlockHashesCorrect_MultiBlockTipset locally that seems to be ✅

[rvagg]

Opened a PR for that flaky test @ #12712