[Bug] UnboundLocalError: local variable 'summary_message' referenced before assignment

### Is this a new bug in dbt-core?

- [X] I believe this is a new bug in dbt-core
- [X] I have searched the existing issues, and I could not find an existing issue for this bug

### Current Behavior

When running `dbt debug` in certain circumstances\*, I get a python stack trace that ends in the following:
```
UnboundLocalError: local variable 'summary_message' referenced before assignment
```

### Expected Behavior

I'd expect a helpful error message relating to the configuration file(s) that were not found (`profiles.yml`) rather that a stack trace.

### Steps To Reproduce

1. Clone and install dbt-core as described in the CONTRIBUTING file
1. Do **not** set up any dbt profiles in `profiles.yml` or create `dbt_project.yml`
2. Run `dbt debug`

### Relevant log output

```
(env) $ dbt debug
13:46:12 Running with dbt=1.8.0-a1
13:46:12 dbt version: 1.8.0-a1
13:46:12 python version: 3.9.18
13:46:12 python path: /Users/dbeatty/projects/dbt-core/env/bin/python
13:46:12 os info: macOS-12.6.1-x86_64-i386-64bit
13:46:12 Encountered an error:
local variable 'summary_message' referenced before assignment
13:46:12 Traceback (most recent call last):
File "/Users/dbeatty/projects/dbt-core/core/dbt/cli/requires.py", line 97, in wrapper
result, success = func(*args, **kwargs)
File "/Users/dbeatty/projects/dbt-core/core/dbt/cli/requires.py", line 82, in wrapper
return func(*args, **kwargs)
File "/Users/dbeatty/projects/dbt-core/core/dbt/cli/main.py", line 420, in debug
results = task.run()
File "/Users/dbeatty/projects/dbt-core/core/dbt/task/debug.py", line 126, in run
load_profile_status: SubtaskStatus = self._load_profile()
File "/Users/dbeatty/projects/dbt-core/core/dbt/task/debug.py", line 213, in _load_profile
profile_names, summary_message = self._choose_profile_names()
File "/Users/dbeatty/projects/dbt-core/core/dbt/task/debug.py", line 292, in _choose_profile_names
return profiles, summary_message
UnboundLocalError: local variable 'summary_message' referenced before assignment
```

Add the following code in the [right place](https://github.com/dbt-labs/dbt-core/blob/2f2e0cee10094270a85c099b4035c4266b1ec926/core/dbt/task/debug.py#L274-L276):

```python
summary_message = f" profile path <{self.profile_path}> not found\n"
```

It will yield another problem to solve:

```
(env) $ dbt debug
13:46:30 Running with dbt=1.8.0-a1
13:46:30 dbt version: 1.8.0-a1
13:46:30 python version: 3.9.18
13:46:30 python path: /Users/dbeatty/projects/dbt-core/env/bin/python
13:46:30 os info: macOS-12.6.1-x86_64-i386-64bit
13:46:30 Using profiles dir at /Users/dbeatty/projects/dbt-core
13:46:30 Using profiles.yml file at /Users/dbeatty/projects/dbt-core/profiles.yml
13:46:30 Using dbt_project.yml file at /Users/dbeatty/projects/dbt-core/dbt_project.yml
13:46:30 Encountered an error:
Internal Error
Profile should not be None if loading profile completed
```

Add the following code in the [right place](https://github.com/dbt-labs/dbt-core/blob/2f2e0cee10094270a85c099b4035c4266b1ec926/core/dbt/task/debug.py#L233-L234):

```python
if len(profile_names) == 0:
profile_errors.append(summary_message)
```

Now it will give the expected output:

```
(env) $ dbt debug
13:46:52 Running with dbt=1.8.0-a1
13:46:52 dbt version: 1.8.0-a1
13:46:52 python version: 3.9.18
13:46:52 python path: /Users/dbeatty/projects/dbt-core/env/bin/python
13:46:52 os info: macOS-12.6.1-x86_64-i386-64bit
13:46:53 Using profiles dir at /Users/dbeatty/projects/dbt-core
13:46:53 Using profiles.yml file at /Users/dbeatty/projects/dbt-core/profiles.yml
13:46:53 Using dbt_project.yml file at /Users/dbeatty/projects/dbt-core/dbt_project.yml
13:46:53 Configuration:
13:46:53 profiles.yml file [ERROR invalid]
13:46:53 dbt_project.yml file [ERROR not found]
13:46:53 Required dependencies:
13:46:53 - git [OK found]

13:46:53 Connection test skipped since no profile was found
13:46:53 2 checks failed:
13:46:53 profile path not found
Profile loading failed for the following reason:
profile path not found

13:46:53 Project loading failed for the following reason:
project path not found
```

### Environment

```markdown
- OS: macOS
- Python: Python 3.9.18
- dbt: 1.8.0-a1
```

### Which database adapter are you using with dbt?

postgres

### Additional Context

Proposed fixes mentioned in the "Relevant log output" section above.