html_render: errorneous <del> surrounding entire body in recent EPA diffs

[Mr0grog]

On recent epa.gov diffs like this one, a <del> element is erroneously surrounding almost the entire page body, including other <del> elements: https://monitoring.envirodatagov.org/page/c5997532-42cf-4748-bbab-7364185a1695/1d6a21b5-48f3-47d8-973f-373d0e8727e9..af4429e2-b696-44d7-a8b5-fd1cc96fa3ec

This is a diff between these bodies:

• https://edgi-wm-archive.s3.amazonaws.com/738fdc28c15e7ceb8f9aec105a3fb4d07c7c2760e16ec3b1e9ad179dde3a17fa
• https://edgi-wm-archive.s3.amazonaws.com/31ff638eaf80af982c42bbd45c2e5b816ef318a1b3f20db38eaca4d83c469fcd

Or:

/html_token?a=https://edgi-wm-archive.s3.amazonaws.com/738fdc28c15e7ceb8f9aec105a3fb4d07c7c2760e16ec3b1e9ad179dde3a17fa&b=https://edgi-wm-archive.s3.amazonaws.com/31ff638eaf80af982c42bbd45c2e5b816ef318a1b3f20db38eaca4d83c469fcd

This is probably an error in merge_change_groups or merge_changes.