Fixes this USBAN error:

../src/sort.d:42:18: runtime error: applying non-zero offset 18446744073709551584 to null pointer

--- src/sort.d.orig	2024-12-28 00:47:59.000000000 -0700
+++ src/sort.d	2025-02-10 09:33:00.121016044 -0700
@@ -39,7 +39,7 @@
 /* sort(v,n); sorts the array v[0]..v[n-1] in ascending order. */
 local void SORT(SORTID,sort) (SORT_ELEMENT* v, uintL n)
 {
-  var SORT_ELEMENT* w = &v[-1];
+  var SORT_ELEMENT* w;
   /* w[1]..w[n] point to the same elements as v[0]..v[n-1] .
      We collect the numbers 1,...,n to a balanced binary subtree,
      so that k has the children 2*k and 2*k+1.
@@ -70,6 +70,7 @@ local void SORT(SORTID,sort) (SORT_ELEME
   }
   if (n<=1) /* nothing to do? */
     return;
+  w = &v[-1];
   { /* Because of 2*(floor(n/2)+1) > n,
        w[floor(n/2)+1]..w[n] is already sorted. */
     var uintL r;