As per the error, it states, cannot read properties of null. So possibly there is a chance that you are deleting the object and its association and loading the object and/or its associations in the target page.
- Redirect to some overview page
- Or use refresh from microflow
In addition to Nirmalkumar’s answer, it sounds like the page is expecting the 1-1 association to be populated, and as it’s not, you’re seeing this error.
Another approach would be to put a container around the fields in the associated object, and conditional visibility on it based on wether the association is empty or not. If it’s empty the object isn’t there, so don’t try to show the content.
I had the exact same error, after a lenghty analysis we found that the error was in the ShowMore widget in the page that is behind the page on which the delete was executed.
After removing the ShowMore widgets the error was gone.
Hope this helps...