Invalid characters for a wallet name, e.g. `bitcoin-qt -wallet=你好` used to result in an error like this

<img width="494" alt="schermafbeelding 2018-07-24 om 17 46 37" src="https://user-images.githubusercontent.com/10217/43150553-7bdf598a-8f6a-11e8-8972-44c311a57e56.png">

But now it just crashes:

<img width="509" alt="schermafbeelding 2018-07-24 om 17 43 26" src="https://user-images.githubusercontent.com/10217/43150605-9cf32192-8f6a-11e8-9333-87d074c8dd35.png">

I didn't do a `git bisect`, but it broke somewhere this year :-)
#include <wallet/wallet.h>
#include <checkpoints.h>
#include <chain.h>
#include <wallet/coincontrol.h>
#include <consensus/consensus.h>
#include <consensus/validation.h>
#include <fs.h>
#include <key.h>
#include <key_io.h>
#include <keystore.h>
#include <validation.h>
#include <net.h>
#include <policy/fees.h>
#include <policy/policy.h>
#include <policy/rbf.h>
#include <primitives/block.h>
#include <primitives/transaction.h>
#include <script/script.h>
#include <shutdown.h>
#include <timedata.h>
#include <txmempool.h>
#include <utilmoneystr.h>
#include <wallet/fees.h>
#include <wallet/walletutil.h>