tpmtool not accepting SRK with no password

Description of problem:

The existing tpmtool should be working with an SRK with no password. Basically it needs a command line option to use an SRK with no password. Currently it prompts for a password and pressing return uses an empty password rather than a null password.

tpm_takeownership --srk-well-known sets the SRK secret to all zeros (20 bytes of zeros)

I know TPM 1.2 is old by now, nevertheless... Maybe we could add the same parameter that tpm_takeownership uses to tpmtool.