This fixes a corner-case in the {NativeModuleSerializer} with modules
that do not contain any functions in the code table.
R=ahaas@chromium.org
TEST=mjsunit/regress/wasm/regress-801850
BUG=chromium:801850
Change-Id: I30cc3a26f30d8653fba2d7b99715830d12300ac2
Reviewed-on: https://chromium-review.googlesource.com/866773
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50581}
