XDP-02 fix Panic In ProcessOrderPending Leads To Chain Halt

[liam-lai]

Proposed changes

In the implementation, if from != acc and len(accTxs) == 1, the key from will be deleted from the map txs, and an empty array accTxs[1:] will be assigned to the key acc. As a result, when the for loop checks the key acc, a panic will occur with the error index out of range [0] with length 0 because the code is trying to get the value of accTxs[0].

Types of changes

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• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation Update (if none of the other choices apply)
• Regular KTLO or any of the maintaince work. e.g code style
• CICD Improvement

Impacted Components

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• Consensus
• Account
• Network
• Geth
• Smart Contract
• External components
• Not sure (Please specify below)

Checklist

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• This PR has sufficient test coverage (unit/integration test) OR I have provided reason in the PR description for not having test coverage
• Provide an end-to-end test plan in the PR description on how to manually test it on the devnet/testnet.
• Tested the backwards compatibility.
• Tested with XDC nodes running this version co-exist with those running the previous version.
• Relevant documentation has been updated as part of this PR
• N/A