Bug report - ssh signing causes git tag -l malloc failed

What did you do before the bug happened? (Steps to reproduce your issue)

When using ssh signing `git tag -l --format='%(contents:body)' <tag>` returns `fatal: Out of memory, malloc failed (tried to allocate 18446744073709551323 bytes)`

What did you expect to happen? (Expected behavior)

The tag to be returned without crashing

What happened instead? (Actual behavior)

git crashed with the above error (`fatal: Out of memory, malloc failed (tried to allocate 18446744073709551323 bytes)`)

What's different between what you expected and what actually happened?

Anything else you want to add:

``` [14:23:54] (0):~/src/github.com/my/repo % git tag -sam v0.0.9 v0.0.9

[14:24:03] (0):~/src/github.com/my/repo % git -c log.showSignature=false tag -l --format='%(contents:body)' v0.0.9 fatal: Out of memory, malloc failed (tried to allocate 18446744073709551323 bytes)

[14:24:27] (0):~/src/github.com/my/repo % git tag -sm v0.0.9-no-annotate v0.0.9-no-annotate

[14:27:19] (0):~/src/github.com/my/repo % git -c log.showSignature=false tag -l --format='%(contents:body)' v0.0.9-no-annotate fatal: Out of memory, malloc failed (tried to allocate 18446744073709551323 bytes)

[14:27:26] (128):~/src/github.com/my/repo % git tag -m v0.0.9-no-annotate-no-ssh v0.0.9-no-annotate-no-ssh

[14:28:10] (0):~/src/github.com/my/repo % git -c log.showSignature=false tag -l --format='%(contents:body)' v0.0.9-no-annotate-no-ssh

```

Please review the rest of the bug report below. You can delete any lines you don't wish to share.

[System Info] git version: git version 2.36.0 cpu: x86_64 no commit associated with this build sizeof-long: 8 sizeof-size_t: 8 shell-path: /bin/sh feature: fsmonitor--daemon uname: Darwin 20.6.0 Darwin Kernel Version 20.6.0: Tue Oct 12 18:33:42 PDT 2021; root:xnu-7195.141.8~1/RELEASE_X86_64 x86_64 compiler info: clang: 13.0.0 (clang-1300.0.29.30) libc info: no libc information available $SHELL (typically, interactive shell): /bin/zsh

[Enabled Hooks]