zink: zero allocate resident_defs array in ntv

this makes assert(def!=0) more reliable

Fixes: 73ef54e342 ("zink: handle residency return value from sparse texture instructions")
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/27414>

src/gallium/drivers/zink/nir_to_spirv/nir_to_spirv.c

@@ -4774,7 +4774,7 @@ nir_to_spirv(struct nir_shader *s, const struct zink_shader_info *sinfo, uint32_
       /* this could be huge, so only alloc if needed since it's extremely unlikely to
        * ever be used by anything except cts
        */
-      ctx.resident_defs = ralloc_array_size(ctx.mem_ctx,
+      ctx.resident_defs = rzalloc_array_size(ctx.mem_ctx,
                                             sizeof(SpvId), entry->ssa_alloc);
       if (!ctx.resident_defs)
          goto fail;