Marja pointed out that the following code causes a Torque crash:

Convert<Smi>(MessageTemplate::kFoo)

This change is a small fix to not crash in that case.

Bug: v8:7793, v8:10475
Change-Id: I7856366856a4cd7facdb19686a2d4c92b0d04516
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2182175Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Commit-Queue: Seth Brenith <seth.brenith@microsoft.com>
Cr-Commit-Position: refs/heads/master@{#67580}