mrz.generator: wrong output when primary id == ""

[Arg0s1080]

I discovered that something similar (comes from #1) happens in mrz.generator. When the primary identifier is not given, an incorrect output is got. For example:

from mrz.generator.td3 import TD3CodeGenerator

print(TD3CodeGenerator("P",           # Document type
                       "Utopia",      # Country
                       "",            # Surname(s)
                       "Anna María",  # Given name(s)
                       "L898902C3",   # Passport number
                       "UTO",         # Nationality
                       "740812",      # Birth date
                       "F",           # Genre
                       "120415",      # Expiry date
                       "ZE184226B"))  # Id number

This wrong output is got:

P<UTO<<ANNA<MARIA<<<<<<<<<<<<<<<<<<<<<<<<<<<
L898902C36UTO7408122F1204159ZE184226B<<<<<10

Originally posted by @Arg0s1080 in #1 (comment)