`ScanForWalletTransactions()` has the following comment about its return value:

```
 * Returns null if scan was successful. Otherwise, if a complete rescan was not
 * possible (due to pruning or corruption), returns pointer to the most recent
 * block that could not be scanned.
```

This is not strictly true. If `abortrescan` is called, then `ScanForWalletTransactions()` will return `nullptr`, even though the scan wasn't successful to the tip.

This in turn causes a minor bug in `importmulti`, where the call doesn't return the correct error and warning about potentially not finding transactions if `abortrescan` was called.

I think the correct fix is for `ScanForWalletTransactions()` to inform the caller that the rescan was aborted.
{
    CTxDestination dest = CKeyID();
    LOCK(m_wallet.cs_wallet);
    m_wallet.AddDestData(dest, "misc", "val_misc");
    m_wallet.AddDestData(dest, "rr0", "val_rr0");
    m_wallet.AddDestData(dest, "rr1", "val_rr1");
    auto values = m_wallet.GetDestValues("rr");
    BOOST_CHECK_EQUAL(values.size(), 2U);
    BOOST_CHECK_EQUAL(values[0], "val_rr0");
    BOOST_CHECK_EQUAL(values[1], "val_rr1");
}
class ListCoinsTestingSetup : public TestChain100Setup