`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.
void SetBroadcastTransactions(bool broadcast) { fBroadcastTransactions = broadcast; }
    
    bool TransactionCanBeAbandoned(const uint256& hashTx) const;
    
    bool AbandonTransaction(interfaces::Chain::Lock& locked_chain, const uint256& hashTx);
    
    bool MarkReplaced(const uint256& originalHash, const uint256& newHash);
    
    static bool Verify(interfaces::Chain& chain, const WalletLocation& location, bool salvage_wallet, std::string& error_string, std::string& warning_string);
    
    static std::shared_ptr<CWallet> CreateWalletFromFile(interfaces::Chain& chain, const WalletLocation& location, uint64_t wallet_creation_flags = 0);
    /**
     * Wallet post-init setup
     * Gives the wallet a chance to register repetitive tasks and complete post-init tasks
     */
    void postInitProcess();
    bool BackupWallet(const std::string& strDest);
    
    void SetHDChain(const CHDChain& chain, bool memonly);
    const CHDChain& GetHDChain() const { return hdChain; }