If a TLV was elementary (no nested IEs), and it had only a single
integer content whose value is 0, we erroneously encoded that as
zero-length TLV (len=0, no value part):
>>> rf = pySim.euicc.RefreshFlag(decoded=0);
>>> rf.to_bytes()
b''
>>> rf.to_tlv()
b'\x81\x00'
After this change it is correct:
>>> rf = pySim.euicc.RefreshFlag(decoded=0);
>>> rf.to_bytes()
b'\x00'
>>> rf.to_tlv()
b'\x81\x01\x00'
Change-Id: I5f4c0555cff7df9ccfc4a56da12766d1bf89122f
0f7d48ed69