Array index out of bounds warning

[NAThompson]

Found in this build log, in particularly:

../../../boost/multiprecision/cpp_int/bitwise.hpp:598:14: warning: array subscript [7, 1152921504606846975] is outside array bounds of 'boost::multiprecision::backends::cpp_bin_float<50>::rep_type [1]' {aka 'boost::multiprecision::backends::cpp_int_backend<168, 168, boost::multiprecision::unsigned_magnitude, boost::multiprecision::unchecked, void> [1]'} [-Warray-bounds=]

  598 |    pr[i] = pr[i + offset] >> shift;

      |            ~~^