After 75d7891ca1
`neo-go` does claim that an empty invocation script is the only way to
fill missing signature for unsigned notary requests. The new notary actor
does it that way and, therefore, breaks notary request parsing by the
Alphabet because of skipping any request that is not filled with a dummy (64
zeros) invocation script. Support both way. The "Dummy" approach will be
dropped later.
Signed-off-by: Pavel Karpy <p.karpy@yadro.com>