Fix invalid grid file raising uncaught exception

[eivindjahren]

Issue
Resolves #8351

• 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 tests pass locally (after every commit!)

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 89.84%. Comparing base (a51790c) to head (70d8c1a).
Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #8352   +/-   ##
=======================================
  Coverage   89.84%   89.84%           
=======================================
  Files         347      346    -1     
  Lines       21138    21094   -44     
=======================================
- Hits        18991    18952   -39     
+ Misses       2147     2142    -5     

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[yngve-sk]

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