cut: avoid a redundant heap allocation

cut: avoid a redundant heap allocation

* src/cut.c (set_fields): Don't allocate memory for
`printable_field' if there are no finite ranges.
This is achieved by keeping max_range_endpoint as 0 when
there are no finite ranges.  max_range_endpoint is then
used throughout the code to guard against allocation of,
and access to the bit array.
The extra allocation was introduced via commit v8.10-3-g2e636af.