Commit
63229953b5eed05e74200629a6dec8ea4600d54f
by pmaier@sysmocom.decommands: do not use b2h with a string
The function h2b expects a bytearray and must not be used on a string.
This is also true for nullstrings ('').
Related: OS#6869
Change-Id: I0e28e6ec476901bf19aa0f8640e41c74aa6e3aa2