Saving hangs on a brookings.edu page

Hi, we've received a [user report](https://forums.zotero.org/discussion/132704/snapshots-cause-browser-to-hang) of a website where saving of a snapshot hangs.

We can reproduce it with both the Zotero Connector and the Chrome SingleFile extension.

https://www.brookings.edu/articles/raj-chetty-in-14-charts-big-findings-on-opportunity-and-mobility-we-should-know/