What is the meaning of the following error?

internal error: get_block_size: none

If you need more details, I may have an example document. I must first get permission from the user.

It is a flex box issue, it would be helpful if you could email me (mikeday@yeslogic.com) a test document so that we can track it down.

I got this error when I accidentally changed the @page margin-top to 1080px on a US-Letter document (it was using flexbox).

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