How can I determine if a field is an array or text?

[daBellows]

I have a situation where I have to concatenate values from a multi-select (where I use the join() function), but if only 1 selection is made my join() returns a null.

I need to find a way to determine if this field is coming in as an array or single text field.

Ideas?

[daBellows · Accepted solution]

FYI - I figured this out by adding in:
add(emptyarray;{field})

...then do the join()