Error: Crystal Reports - "errorKind"

I have a report made in Crystal Reports. The report works well, but this error appears when generating the report:

According to the error message, an error is shown in the formula that I give below:

if {registros1.subcartera}= 'CARTA 1'
then "PRIMER AVISO DE COBRANZA"
else 
if {registros1.subcartera}= 'CARTA 2'
then "SEGUNDO AVISO DE COBRANZA"
else 
    if {registros1.subcartera}= 'CARTA 3'
    then "TERCER AVISO DE COBRANZA"
    else 
        if {registros1.subcartera}='CARTA NOTARIAL' or {registros1.subcartera}='NOTARIAL'
        then 'CARTA NOTARIAL'

The information I extracted from a MySQL database, but in this I have no problems since the information does arrive.

[Edit] Attach URL to the source code on Github: link

[Edit] Report: