The MemoryInitImmediate and TableInitImmediate read a Memory/Table
index, followed by a segment index. If reading the first index fails, we
need to stop reading, or the decoder will read past the end.

Bug: chromium:907324
Change-Id: I3eb46c08d03e3b2e44ed4081d307b32c799abcec
Reviewed-on: https://chromium-review.googlesource.com/c/1351502
Commit-Queue: Ben Smith <binji@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57889}