Fix PHP8.1 repeated notice errors in Table.tpl

[artfulrobot]

Overview

Simple smarty .tpl fix.

Before

The smarty template assumed an array key exists that often doesn't, resulting in lots of errors (gets processed for every row of a table!)

After

Missing key handled silently via |default:""

[civibot]

Thank you for contributing to CiviCRM! ❤️ We will need to test and review the PR. 👷

Introduction for new contributors

• If this is your first PR, an admin will greenlight automated testing with the command ok to test or add to whitelist.
• A series of tests will automatically run. You can see the results at the bottom of this page (if there are any problems, it will include a link to see what went wrong).
• A demo site will be built where anyone can try out a version of CiviCRM that includes your changes.
• If this process needs to be repeated, an admin will issue the command test this please to rerun tests and build a new demo site.
• Before this PR can be merged, it needs to be reviewed. Please keep in mind that reviewers are volunteers, and their response time can vary from a few hours to a few weeks depending on their availability and their knowledge of this particular part of CiviCRM.
• A great way to speed up this process is to "trade reviews" with someone - find an open PR that you feel able to review, and leave a comment like "I'm reviewing this now, could you please review mine?" (include a link to yours). You don't have to wait for a response to get started (and you don't have to stop at one!) the more you review, the faster this process goes for everyone 😄
• To ensure that you are credited properly in the final release notes, please add yourself to contributor-key.yml
• For more information about contributing, see CONTRIBUTING.md.

Quick links for reviewers

• ➡️ Demo site for this PR
• 📖 Review standards
• 🗒️ Review template (brief or verbose)