Review the way the program constructs the sqlda and related data structures; somehow it is setting up a null pointer. The error might be caused by using a row or collection host variable without having executed the necessary ALLOCATE statement.
If the program is in IBM Informix 4GL or another language in which the sqlda is not constructed directly by the program, or if this statement refers only to host variables by name, this error should not occur. If the error recurs, note all circumstances and contact IBM Informix Technical Support.