None of Henry's patches are in bzr.dev 2481, so it hasn't been merged into the core. bzr does give a warning when merging into an empty branch:
bzr: ERROR: This branch has no commits. (perhaps you would prefer 'bzr pull')
Performing a pull succeeds. That would seem to be sufficient - use pull in this situation instead of merge.
None of Henry's patches are in bzr.dev 2481, so it hasn't been merged into the core.
bzr does give a warning when merging into an empty branch:
bzr: ERROR: This branch has no commits. (perhaps you would prefer 'bzr pull')
Performing a pull succeeds.
That would seem to be sufficient - use pull in this situation instead of merge.