[BUG] Index Error when installing app with service setting and no existing services

[jakeymac]

Describe the bug
When attempting to install an app with a service setting and no existing services. the following error comes up:

File "/home/jjohnson/miniforge3/envs/test_services/bin/tethys", line 6, in
sys.exit(tethys_command())
~~~~~~~~~~~~~~^^
File "/home/jjohnson/erdc_project/migrations/tethys/tethys_cli/init.py", line 76, in tethys_command
args.func(args)
~~~~~~~~~^^^^^^
File "/home/jjohnson/erdc_project/migrations/tethys/tethys_cli/install_commands.py", line 923, in install_command
run_interactive_services(app_name)
~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^
File "/home/jjohnson/erdc_project/migrations/tethys/tethys_cli/install_commands.py", line 458, in run_interactive_services
services = services_list_command(args)[0]
~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^
IndexError: list index out of range

To Reproduce
Steps to reproduce the behavior:

1. Scaffold a new app in a clean Tethys environment with no services created.
2. Add a service setting to the app.py file
3. Run tethys install inside the app's directory

Expected behavior
The app should install and let the user know that the service setting will need to be assigned.

[Muhtasim-Munif-Fahim]

This appears to be fixed on main (a5fa18e).

The [0] from the traceback is gone — run_interactive_services now flattens the result instead of indexing it:

services = [
    service
    for service_group in services_list_command(args)
    for service in service_group
]

if len(services) <= 0:
    write_warning(
        "No compatible services found. See:\n\n  tethys services create {} -h\n".format(
            get_setting_type(setting)
        )
    )
    continue

So an empty service list can no longer raise IndexError, and the behaviour matches what the issue asks for: a warning naming the setting, then the install continues rather than aborting.

grep -n "services_list_command(args)\[0\]" tethys_cli/*.py returns nothing.

Flagging rather than opening an empty PR — this looks closeable.