[conformal/btcscript] 3aaafb: handle op_checksig with an empty signature on the ...

[Owain G. Ainsworth]

  Branch: refs/heads/master
  Home:   https://github.com/conformal/btcscript
  Commit: 3aaafbd7faafcb5a5b5e5ec4f208224df3abbb6e
      
https://github.com/conformal/btcscript/commit/3aaafbd7faafcb5a5b5e5ec4f208224df3abbb6e
  Author: Owain G. Ainsworth <o...@conformal.com>
  Date:   2013-11-07 (Thu, 07 Nov 2013)

  Changed paths:
    M opcode.go

  Log Message:
  -----------
  handle op_checksig with an empty signature on the stack.

Crash found by jy-p, fix by me.