Concatenation containing a "null" term

["Pierre Thibaudeau" <pierdeux(at)gmail(dot)com>]

(I am certain I once saw the answer to the following question, but I can't for the life of me find out where!)

I create a View as

SELECT (firstname || ' ' || lastname)::character(50) AS fullname
FROM name_table;

firstname and lastname are text columns, and firstname may be null.

Unfortunately, it seems that whenever firstname is null, the resulting fullname is null also.  Is there a way of having the null-strings terms of the concatenation operator be considered as empty strings instead?

Thanks for the help!