Safari: fix site editor template error

[ellatrix]

What?

See #66579 (comment).

There must be some kind of race condition that that PR surfaced in Safari, so this serves as a temporary fix while I investigate the issue.

Why?

How?

Testing Instructions

Testing Instructions for Keyboard

Screenshots or screencast

[github-actions]

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Co-authored-by: ellatrix <ellatrix@git.wordpress.org>
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[mcsf]

Thanks, Speedy!

[github-actions]

Flaky tests detected in 338b51b.
Some tests passed with failed attempts. The failures may not be related to this commit but are still reported for visibility. See the documentation for more information.

🔍 Workflow run URL: https://github.com/WordPress/gutenberg/actions/runs/11616617361
📝 Reported issues:

• [Flaky Test] can be replaced by dragging-and-dropping images from the inserter #50325 in /test/e2e/specs/editor/blocks/image.spec.js