tox: Using non-existent environment does not fail

Issue

Using an environment that does not exist still executes without failure but does nothing useful.

Environment

Provide at least:

• OS: Linux
• pip list of the host Python where tox is installed:

Package       Version
------------- -------
cachetools    5.2.1
chardet       5.1.0
colorama      0.4.6
distlib       0.3.6
filelock      3.9.0
packaging     23.0
pip           22.3.1
platformdirs  2.6.2
pluggy        1.0.0
pyproject_api 1.4.0
setuptools    65.7.0
tomli         2.0.1
tox           4.2.8
virtualenv    20.17.1
wheel         0.38.4

Minimal example

If possible, provide a minimal reproducer for the issue:

tox run -e abcdefg