message: strptime now fails with empty format string
diff: @@ -180,15 +180,11 @@ WHERE rt <> dt
  ----
  # empty specifier and string
  -query I
  +statement error
  SELECT strptime('', '')
  -----
  -1900-01-01 00:00:00
  -query I
  +statement error
  SELECT strptime(NULL, '')
  -----
  -NULL
  query I
  SELECT strptime('', NULL)
  