According to comments inside SNMPv2-SMI, zeroDotZero is used as “a value used for null identifiers”. However, when I tested #SNMP against Microsoft SNMP agent for Windows Vista Home Basic, I found that this agent returned ccitt when the identifier is null.
I didn’t have chance to test other agents, so I don’t know whether right now I need to fix #SNMP to replace occurrences of ccitt with zeroDotZero. But this issue is logged here as #2366 under Issue Tracker.