Avoid possible UnboundLocalError for end_event

[berland]

The error has been observed to occur in the log. Not trying to display further error messages to why it is None.

Issue
Resolves #my_issue

Approach
Short description of the approach

(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 'pytest tests/ert/unit_tests -n logical -m "not integration_test"')

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

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.38%. Comparing base (4321e49) to head (ed3c27f).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #8843      +/-   ##
==========================================
- Coverage   91.40%   91.38%   -0.02%     
==========================================
  Files         342      342              
  Lines       21034    21035       +1     
==========================================
- Hits        19226    19223       -3     
- Misses       1808     1812       +4     

Flag	Coverage Δ
cli-tests	39.61% <100.00%> (-0.02%)	⬇️
gui-tests	73.56% <100.00%> (+<0.01%)	⬆️
performance-tests	50.19% <100.00%> (-0.05%)	⬇️
unit-tests	79.84% <100.00%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[andreas-el]

✈️