fix: Handle case where Deadline Cloud Submitter is opened from unsaved scene

[jlangmann-aws]

What was the problem/requirement? (What/Why)

Opening up the Deadline Cloud Submitter from a blank script presented the following error:

Exception caught:
Traceback (most recent call last):
  File "/home/rocky/git/deadline-cloud/src/deadline/client/ui/__init__.py", line 38, in gui_error_handler
    yield
  File "/home/rocky/git/deadline-cloud-for-nuke/src/deadline/nuke_submitter/deadline_submitter_for_nuke.py", line 36, in show_nuke_render_submitter_noargs
    return show_nuke_render_submitter(mainwin)
  File "/home/rocky/git/deadline-cloud-for-nuke/src/deadline/nuke_submitter/deadline_submitter_for_nuke.py", line 188, in show_nuke_render_submitter
    render_settings.load_sticky_settings(get_nuke_script_file())
  File "/home/rocky/git/deadline-cloud-for-nuke/src/deadline/nuke_submitter/data_classes.py", line 38, in load_sticky_settings
    sticky_settings_filename = Path(scene_filename).with_suffix(
  File "/opt/nuke/Nuke14.0v5/lib/python3.9/pathlib.py", line 903, in with_suffix
    raise ValueError("%r has an empty name" % (self,))
ValueError: PosixPath('.') has an empty name

What was the solution? (How)

If the script name is empty, present the user with an error.

What is the impact of this change?

Handle the case where user opens the deadline cloud submitter from an unsaved script.

How was this change tested?

Yes

Did you run the "Job Bundle Output Tests"? If not, why not? If so, paste the test results here.

Timestamp: 2023-09-20T22:37:07.916822+00:00
Running job bundle output test: /home/rocky/git/deadline-cloud-for-nuke/job_bundle_output_tests/multi-load-save

multi-load-save
Test succeeded

Timestamp: 2023-09-20T22:37:08.247677+00:00
Running job bundle output test: /home/rocky/git/deadline-cloud-for-nuke/job_bundle_output_tests/noise-saver

noise-saver
Test succeeded

Timestamp: 2023-09-20T22:37:08.443511+00:00
Running job bundle output test: /home/rocky/git/deadline-cloud-for-nuke/job_bundle_output_tests/cwd-path

cwd-path
Test succeeded

Timestamp: 2023-09-20T22:37:08.650688+00:00
Running job bundle output test: /home/rocky/git/deadline-cloud-for-nuke/job_bundle_output_tests/ocio

ocio
Test succeeded

All tests passed, ran 4 total.
Timestamp: 2023-09-20T22:37:11.037997+00:00

Was this change documented?

No, bug fix.

Is this a breaking change?

No