Error importing exported payment accounts
Importing exported payment accounts sometimes fails with an error.

I have not been able to recreate the error. Maybe it only happens with specific payment accounts.

```
Aug.-16 01:48:15.785 [JavaFX Application Thread] INFO  h.n.p.p.PeerManager: We have 12 connections open. Our limit is 12 
Aug.-16 01:53:57.639 [JavaFX Application Thread] INFO  h.c.u.Profiler: Total memory: 125 MB; Used memory: 65,605 MB; Free memory: 59,395 MB; Max memory: 1 GB; No. of threads: 83 
Aug.-16 01:58:56.402 [PersistenceManager-read-FiatPaymentAccounts] WARN  h.c.p.PersistenceManager: Expected encrypted persisted file, attempting to getPersisted without decryption 
Aug.-16 01:58:56.403 [PersistenceManager-read-FiatPaymentAccounts] ERROR h.c.p.PersistenceManager: Reading FiatPaymentAccounts failed with Protocol message tag had invalid wire type.. 
Aug.-16 01:58:56.404 [PersistenceManager-read-FiatPaymentAccounts] ERROR h.c.app.DevEnv: com.google.protobuf.InvalidProtocolBufferException$InvalidWireTypeException: Protocol message tag had invalid wire type. 
Aug.-16 01:58:58.733 [InputHandler-bi6zlsppjx73...] WARN  h.n.p.n.Connection: proto is null because protoInputStream.read()=-1 (EOF). That is expected if client got stopped without proper shutdown. 
Aug.-16 01:59:18.734 [PersistenceManager-read-CryptoPaymentAccounts] WARN  h.c.p.PersistenceManager: Expected encrypted persisted file, attempting to getPersisted without decryption 
Aug.-16 01:59:18.738 [PersistenceManager-read-CryptoPaymentAccounts] ERROR h.c.p.PersistenceManager: Reading CryptoPaymentAccounts failed with While parsing a protocol message, the input ended unexpectedly in the middle of a field.  This could mean either that the input has been truncated or that an embedded message misreported its own length.. 
Aug.-16 01:59:18.738 [PersistenceManager-read-CryptoPaymentAccounts] ERROR h.c.app.DevEnv: com.google.protobuf.InvalidProtocolBufferException: While parsing a protocol message, the input ended unexpectedly in the middle of a field.  This could mean either that the input has been truncated or that an embedded message misreported its own length. 
Aug.-16 01:59:33.970 [Connection] INFO  h.n.p.p.PeerManager: Num of latestLivePeers=10
```

This issue requests reproducing the error and fixing it.