Avoid raising runtime error when calling get_opt_status and no objectives and controls are stored in everest storage

[DanSava]

Issue
Resolves #10155

Approach
Return empty dict if no objectives and controls are stored in everest storage when calling get_opt_status

(Screenshot of new behavior in GUI if applicable)

• PR title captures the intent of the changes, and is fitting for release notes.
• Added appropriate release note label
• Commit history is consistent and clean, in line with the contribution guidelines.
• Make sure unit tests pass locally after every commit (git rebase -i main --exec 'just rapid-tests')

When applicable

• When there are user facing changes: Updated documentation
• New behavior or changes to existing untested code: Ensured that unit tests are added (See Ground Rules).
• Large PR: Prepare changes in small commits for more convenient review
• Bug fix: Add regression test for the bug
• Bug fix: Create Backport PR to latest release

[codspeed-hq]

CodSpeed Performance Report

Merging #10156 will improve performances by 13.65%

_{Comparing DanSava:update-get-opt-status (c2d62a8) with main (8025e0b)}

Summary

⚡ 1 improvements
✅ 24 untouched benchmarks

Benchmarks breakdown

	Benchmark	BASE	HEAD	Change
⚡	test_direct_dark_performance_with_storage[gen_x: 20, sum_x: 20 reals: 10-summary-get_record_observations]	1.5 ms	1.3 ms	+13.65%

[yngve-sk]

Overall looks good, I think get_opt_status is always invoked after an optimization run, and if there are no objectives in storage we can raise an explicit error about it.

[yngve-sk]

LGTM, I think erroring explicitly from within _get_opt_status is not feasible afterall since it is invoked during the optimization run. We should however give an explicit error if there are no objective results after running the optimization, but that is a for a separate PR.