Error message:Array Index out of bound

Hi, Would you please tell me how to fix this problem?

In the form, there are 4 fields: person1,person2,person3,Person4, I used a PersonTotal field(it is computed field) to include the 4 fields. foluma like that:

Field PersonTotal:=@Trim(@Unique(Person1:person2:person3:person4)), some of the Person1,2,3,4 are multiple values, some of them are not, but they have values in the field. why I get error message “Array Indes out of bound” sometimes in the PersonTotal field?

Thanks a lot.

Linda

Subject: Error message:Array Index out of bound.