Newbie: Lisp error handling question

This is part of a bigger lisp. I am still not familiar how to use error
handling.
On occassion when I run c:t66 there is no text to be found, so it gives me
an
error ; error: bad argument type: lselsetp nil
When I run
(if txt (c:t55)(C:T66))
the lisp will crash.
How can I avoid this?
(defun C:t66 () (setq txt (cdr (assoc 1 (entget (ssname (ssget "x" '((0 .
"TEXT") (62 . 41))) 0))))))
(defun C:xtt () ;beginning of a bigger lisp
(if txt (c:t55)(C:T66))
.......