gcc warns against passing a nullptr to a printf '%s' string print, and
the default args of varint consuming functions in the wasm decoder were
providing a null name.

Bug: chromium:1307180
Change-Id: I7a4e7a38119c2568025a597423d391a7c2c573f2
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3735123
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Auto-Submit: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/main@{#81441}