Reported by @kallewoof here: https://github.com/bitcoin/bitcoin/pull/13917#issuecomment-412459298

```
$ ./bitcoin-cli createpsbt "[]" "[{\"$(./bitcoin-cli getnewaddress)\":0.01}]"
cHNidP8BACoCAAAAAAFAQg8AAAAAABepFG6Rty1Vk+fUOR4v9E6R6YXDFkHwhwAAAAAAAA==
$ ./bitcoin-cli decodepsbt cHNidP8BACoCAAAAAAFAQg8AAAAAABepFG6Rty1Vk+fUOR4v9E6R6YXDFkHwhwAAAAAAAA==
error code: -22
error message:
TX decode failed CDataStream::read(): end of data: unspecified iostream_category error
```

struct CMutableTransaction;
class SigningProvider
{
public:
    virtual ~SigningProvider() {}
    virtual bool GetCScript(const CScriptID &scriptid, CScript& script) const { return false; }
    virtual bool GetPubKey(const CKeyID &address, CPubKey& pubkey) const { return false; }
    virtual bool GetKey(const CKeyID &address, CKey& key) const { return false; }
};
extern const SigningProvider& DUMMY_SIGNING_PROVIDER;
class PublicOnlySigningProvider : public SigningProvider
{
private:
    const SigningProvider* m_provider;
public:
    PublicOnlySigningProvider(const SigningProvider* provider) : m_provider(provider) {}
    bool GetCScript(const CScriptID &scriptid, CScript& script) const;
    bool GetPubKey(const CKeyID &address, CPubKey& pubkey) const;
};
struct FlatSigningProvider final : public SigningProvider
{
    std::map<CScriptID, CScript> scripts;
    std::map<CKeyID, CPubKey> pubkeys;
    std::map<CKeyID, CKey> keys;
    bool GetCScript(const CScriptID& scriptid, CScript& script) const override;
    bool GetPubKey(const CKeyID& keyid, CPubKey& pubkey) const override;
    bool GetKey(const CKeyID& keyid, CKey& key) const override;
};
FlatSigningProvider Merge(const FlatSigningProvider& a, const FlatSigningProvider& b);
class BaseSignatureCreator {