Fixes this UBSAN error:

runtime error: variable length array bound evaluates to non-positive value 0

--- src/io.d.orig	2024-12-28 00:47:59.000000000 -0700
+++ src/io.d	2025-02-10 09:50:29.262067759 -0700
@@ -8158,7 +8158,7 @@ local maygc void pr_array (const gcv_obj
     LEVEL_CHECK;
     {         /* determine rank and fetch dimensions and sub-product: */
       var uintL r = (uintL)Iarray_rank(obj); /* rank */
-      var DYNAMIC_ARRAY(dims_sizes,array_dim_size_t,r); /* dynamically allocated array */
+      var DYNAMIC_ARRAY(dims_sizes,array_dim_size_t,r?r:1); /* dynamically allocated array */
       iarray_dims_sizes(obj,dims_sizes);                /* fill */
       var uintL depth = r;          /* depth of recursion */
       var pr_array_locals_t locals; /* local variables */