bug: asdf install returns error for system version

[rnestler]

Describe the Bug

When having configured some tools to use the system versions, asdf install will report an error and return an exit code.

Steps to Reproduce

1. Set a version to system in ~/.too-versions`
2. Run asdf install

Expected Behaviour

Just state that the system version is available.

Actual Behaviour

It shows the error message and returns an error code:

$ asdf install
uninstallable version: system
$ echo $?
1

Environment

asdf info
OS:
Linux renovigi 6.12.12-1-lts #1 SMP PREEMPT_DYNAMIC Sat, 01 Feb 2025 18:47:29 +0000 x86_64 GNU/Linux

SHELL:
zsh 5.9 (x86_64-pc-linux-gnu)

BASH VERSION:
5.2.37(1)-release

ASDF VERSION:
0.16.2-arch

ASDF INTERNAL VARIABLES:
ASDF_DEFAULT_TOOL_VERSIONS_FILENAME=.tool-versions
ASDF_DATA_DIR=/home/raphael/.asdf
ASDF_CONFIG_FILE=/home/raphael/.asdfrc

ASDF INSTALLED PLUGINS:
elixir    https://github.com/asdf-vm/asdf-elixir.git      ea842831ae39417f2dfe7b96fb0c3cc573314aa6
erlang    https://github.com/asdf-vm/asdf-erlang.git      0e617b61ece7cff73331aacc1cd9986e35618c41
flutter   https://github.com/oae/asdf-flutter.git         d73606641938341b8b17bd3e2859a5267bb89bd0
java      https://github.com/halcyon/asdf-java.git        65b6803b53b13d40ae23a08942cde3974f19fcc1
nodejs    https://github.com/asdf-vm/asdf-nodejs.git      93bd217ba74f05080eebb7d8e1c146a385b01d7f
pnpm      https://github.com/jonathanmorley/asdf-pnpm.git 032ae1a9c3f59f87af20ed00da0b873e1322173e
python    https://github.com/danhper/asdf-python.git      a3a01856098d6d2b9642e382f5b38e70275726d1
ruby      https://github.com/asdf-vm/asdf-ruby.git        98e32b9c38e146b164d651c96ccb6d5fa4c3af90
yarn      https://github.com/twuni/asdf-yarn.git          376c5407ef22c82fa56e4bd9f6a9108354063acb

asdf plugins affected (if relevant)

No response