how to null check a null check? aka probably doing something stupid

Hello Appian community,

so I have a long list of codes that I need to be able to search from all of the values have an "entity" more have a "entityType" and some have an "entitySubtype" so I am trying to do a for each loop on all of them and show the enitity for all and the enity+  entityType for those that have it and the enity+  entityType + entitySubtype for those that have all three.

so I have a problem with my null check. I realize that is empty which is why I am using a null check on it. Is there just something obvious that I am not seeing?

here is my error msg:

here is my code:

a!forEach(
                        items: local!symbolIcon,
                        expression: 
                        if(
                          rule!APN_isEmpty(fv!item.entityType),
                          fv!item.entity,
                          if(
                            rule!APN_isEmpty(fv!item.entitySubType),
                            fv!item.entity & " - " & fv!item.entityType,
                            fv!item.entity & " - " & fv!item.entityType & " - " & fv!item.entitySubtype
                          )
                        )
                      ),

what am I not seeing? I have checked the fact that the that entityType is a text object 

I have triple checked the spelling of it. 

all of the values are there. 

what else can I check?

thanks in advance for your assistance