Unable to add plugins through the CLI

**Describe the bug**

When attempting to add a plugin using the CLI, the output is received :

`[INFO] Adding:
sed: -e expression #1, char 0: no previous regular expression`

**Steps to reproduce**

Add a plugin using the CLI, e.g.: `asdf-plugin-manager add shellcheck`

**Expected behavior**

The plugin is added to the internal list of plugins

**Screenshots**


**Additional context**

All pre-reqs are installed.
Environment:
OS: Ubuntu 24.04 noble
Kernel: x86_64 Linux 5.15.167.4
Shell: zsh 5.9
Asdf v0.14.1
Asdf-plugin-manager v1.4.0

Start by reproducing `asdf-plugin-manager add shellcheck` in the stated Ubuntu and zsh environment, then trace the CLI path that updates the internal plugin list and the command producing the sed error. Done means the command completes without the sed message and `shellcheck` appears in the internal plugin list.

Written by the indexing model from the issue text.