ppcsuite/ppcd-old: mempool.go; 10 LoC

Found a possible issue in [ppcsuite/ppcd-old](https://www.github.com/ppcsuite/ppcd-old) at [mempool.go](https://github.com/ppcsuite/ppcd-old/blob/97f7567be8991360a7f5f2a4a100f9d0b0a42cb7/mempool.go#L454-L463)

Below is the message reported by the analyzer for this snippet of code. Beware that the analyzer only reports the first
issue it finds, so please do not limit your consideration to the contents of the below message.

> reference to txHash is reassigned at line 456

[Click here to see the code in its original context.](https://github.com/ppcsuite/ppcd-old/blob/97f7567be8991360a7f5f2a4a100f9d0b0a42cb7/mempool.go#L454-L463)

Click here to show the 10 line(s) of Go which triggered the analyzer.

```go
for txHash := range mp.orphans {
if foundHash == nil {
foundHash = &txHash
}
txHashNum := blockchain.ShaHashToBig(&txHash)
if txHashNum.Cmp(randHashNum) > 0 {
foundHash = &txHash
break
}
}

```

Leave a reaction on this issue to contribute to the project by classifying this instance as a **Bug** :-1:, **Mitigated** :+1:, or **Desirable Behavior** :rocket:
See the descriptions of the classifications [here](https://github.com/github-vet/rangeclosure-findings#how-can-i-help) for more information.

commit ID: 97f7567be8991360a7f5f2a4a100f9d0b0a42cb7

Start by reading mempool.go at lines 454-463 and the surrounding orphan-transaction logic. Check how the range variable txHash is referenced after assignment and whether the analyzer's reported reassignment can affect foundHash. Done means deciding whether this is a bug and correcting the behavior if needed, with relevant validation from the project.

Written by the indexing model from the issue text.