reftable/table: fix OOB read on truncated table #28784

Job	Run time
config	8s
fuzz smoke test	1m 2s
win build	2m 8s
win+Meson build	4m 46s
static-analysis	5m 33s
sparse	3m 44s
osx-reftable (macos-14)	21m 20s
osx-gcc (macos-14)	17m 22s
osx-clang (macos-14)	16m 14s
rust-analysis	1m 25s
documentation	6m 59s
osx-meson (macos-14)	25m 41s
linux-meson (ubuntu:rolling)	13m 43s
linux-musl-meson (alpine:latest)	7m 54s
linux-reftable-leaks (ubuntu:rolling)	30m 44s
linux-asan-ubsan (ubuntu:rolling)	1m 16s
linux-reftable (ubuntu:rolling)	1m 17s
almalinux-8 (almalinux:8)	13m 39s
linux32 (i386/ubuntu:focal)	10m 27s
linux-sha256 (ubuntu:rolling)	1m 23s
linux-leaks (ubuntu:rolling)	24m 36s
linux-breaking-changes (ubuntu:rolling)	12m 39s
linux-TEST-vars (ubuntu:20.04)	13m 38s
debian-11 (debian:11)	8m 39s
fedora-breaking-changes-meson (fedora:latest)	9m 32s
win+VS build	-1s
win+VS test	-1s
win test	-1s
win+Meson test (0)	9m 41s
win+Meson test (3)	5m 41s
win+Meson test (8)	8m 47s
win+Meson test (5)	9m 49s
win+Meson test (7)	6m 27s
win+Meson test (4)	6m 33s
win+Meson test (6)	12m 32s
win+Meson test (2)	10m 59s
win+Meson test (9)	7m 53s
win+Meson test (1)	10m 28s
	5h 44m 36s

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