#339 Seeding vat with empty source gives non-informative errormsg

[wooyay]

pragma.syntax("0.9")
introducer.onTheAir()
def seedVatAuthor := <elang:interp.seedVatAuthor>(<unsafe>).virtualize((introducer))
def scriptSource:=""
def [scriptObj, vat] := seedVatAuthor(scriptSource)

Returns:
--vvvv--
Failed: May not re-register null for swissHash: 354262612305753302611379463302838927054711782208

Maybe change this to something easier to understand?

[wooyay]

Logged In: YES
user_id=1398703
Originator: YES

p.s.: this is maybe important when letting users enter code to be executed in a vat. If the user code does not return anything, this error pops up, not very user friendly
Martin