As reported in Bug 37368, patron searches break if there are patrons with no firstname AND no surname. We often use the create_superlibrarian.pl script to create Koha admin users. Sometimes we forget to edit the patron record and add a firstname/surname. That's now causing these errors as seen in Bug 37368. create_superlibrarian.pl should accept firstname and surname parameters and require at least one of either.
When name not provided we may use uppercase userid My 2c