Fix a confusing amcheck corruption message.
Don't complain about the last TOAST chunk number being different
from what we expected if there are no TOAST chunks at all.
In such a case, saying that the final chunk number is 0 is not
really accurate, and the fact the value is missing from the
TOAST table is reported separately anyway.
Mark Dilger
Discussion: http://postgr.es/m/
AA5506CE-7D2A-42E4-A51D-
358635E3722D@enterprisedb.com