PDF Export Unknown Error (possibly linked to copy+paste tables

[Ethanb00]

Describe the bug
Hey mate.

I was working up some documentation where I was copying and pasting content from the Salesforce Setup/Admin section (basically, tables of permissions, see below). They copy and paste ok, but when I go to export to PDF, it throws the "An unknown error occurred" message.

Many thanks,
Ethan

Steps To Reproduce
Steps to reproduce the behavior:

1. Using Salesforce Setup/Admin section, copy and paste a value/checkbox table into Bookstack
2. Clean up table sizing for aesthetics.
3. Save the page
4. Export to PDF
5. See error

I reviewed some of the previously reported PDF issues and the suggested composer install + cache clears didn't help. I think it's pretty unlikely to be the issue. Other pages export to PDF just fine.
Expected behavior
A PDF export

Screenshots

Your Configuration (please complete the following information):

• Exact BookStack Version (Found in settings): BookStack v0.25.1
• PHP Version: PHP 7.0.33-0ubuntu0.16.04.2
• Hosting Method (Nginx/Apache/Docker): Apache

Additional context
Laravel.log:

production.ERROR: Call to a member function get_cellmap() on null {"userId":1,"email":"[REDACTED]","exception":"[object] (Symfony\Component\Debug\Exception\FatalThrowableError(code: 0): Call to a member $
[stacktrace]
#0 /var/www/bookstack/vendor/dompdf/dompdf/src/FrameDecorator/AbstractFrameDecorator.php(895): Dompdf\FrameReflower\TableCell->reflow(NULL)
#1 /var/www/bookstack/vendor/dompdf/dompdf/src/FrameReflower/TableRow.php(52): Dompdf\FrameDecorator\AbstractFrameDecorator->reflow()
#2 /var/www/bookstack/vendor/dompdf/dompdf/src/FrameDecorator/AbstractFrameDecorator.php(895): Dompdf\FrameReflower\TableRow->reflow(Object(Dompdf\FrameDecorator\Block))
#3 /var/www/bookstack/vendor/dompdf/dompdf/src/FrameReflower/Block.php(845): Dompdf\FrameDecorator\AbstractFrameDecorator->reflow(Object(Dompdf\FrameDecorator\Block))
#4 /var/www/bookstack/vendor/dompdf/dompdf/src/FrameDecorator/AbstractFrameDecorator.php(895): Dompdf\FrameReflower\Block->reflow(Object(Dompdf\FrameDecorator\Block))
#5 /var/www/bookstack/vendor/dompdf/dompdf/src/FrameReflower/Block.php(845): Dompdf\FrameDecorator\AbstractFrameDecorator->reflow(Object(Dompdf\FrameDecorator\Block))
#6 /var/www/bookstack/vendor/dompdf/dompdf/src/FrameDecorator/AbstractFrameDecorator.php(895): Dompdf\FrameReflower\Block->reflow(Object(Dompdf\FrameDecorator\Block))
#7 /var/www/bookstack/vendor/dompdf/dompdf/src/FrameReflower/Block.php(845): Dompdf\FrameDecorator\AbstractFrameDecorator->reflow(Object(Dompdf\FrameDecorator\Block))
#8 /var/www/bookstack/vendor/dompdf/dompdf/src/FrameDecorator/AbstractFrameDecorator.php(895): Dompdf\FrameReflower\Block->reflow(Object(Dompdf\FrameDecorator\Block))
#9 /var/www/bookstack/vendor/dompdf/dompdf/src/FrameReflower/Block.php(845): Dompdf\FrameDecorator\AbstractFrameDecorator->reflow(Object(Dompdf\FrameDecorator\Block))
#10 /var/www/bookstack/vendor/dompdf/dompdf/src/FrameDecorator/AbstractFrameDecorator.php(895): Dompdf\FrameReflower\Block->reflow(Object(Dompdf\FrameDecorator\Block))
#11 /var/www/bookstack/vendor/dompdf/dompdf/src/FrameReflower/Block.php(845): Dompdf\FrameDecorator\AbstractFrameDecorator->reflow(Object(Dompdf\FrameDecorator\Block))
#12 /var/www/bookstack/vendor/dompdf/dompdf/src/FrameDecorator/AbstractFrameDecorator.php(895): Dompdf\FrameReflower\Block->reflow(Object(Dompdf\FrameDecorator\Block))
#13 /var/www/bookstack/vendor/dompdf/dompdf/src/FrameReflower/Block.php(845): Dompdf\FrameDecorator\AbstractFrameDecorator->reflow(Object(Dompdf\FrameDecorator\Block))
#14 /var/www/bookstack/vendor/dompdf/dompdf/src/FrameDecorator/AbstractFrameDecorator.php(895): Dompdf\FrameReflower\Block->reflow(Object(Dompdf\FrameDecorator\Block))
#15 /var/www/bookstack/vendor/dompdf/dompdf/src/FrameReflower/Block.php(845): Dompdf\FrameDecorator\AbstractFrameDecorator->reflow(Object(Dompdf\FrameDecorator\Block))
#16 /var/www/bookstack/vendor/dompdf/dompdf/src/FrameDecorator/AbstractFrameDecorator.php(895): Dompdf\FrameReflower\Block->reflow(Object(Dompdf\FrameDecorator\Block))
#17 /var/www/bookstack/vendor/dompdf/dompdf/src/FrameReflower/Block.php(845): Dompdf\FrameDecorator\AbstractFrameDecorator->reflow(Object(Dompdf\FrameDecorator\Block))
#18 /var/www/bookstack/vendor/dompdf/dompdf/src/FrameDecorator/AbstractFrameDecorator.php(895): Dompdf\FrameReflower\Block->reflow(NULL)
#19 /var/www/bookstack/vendor/dompdf/dompdf/src/FrameReflower/Page.php(141): Dompdf\FrameDecorator\AbstractFrameDecorator->reflow()
#20 /var/www/bookstack/vendor/dompdf/dompdf/src/FrameDecorator/AbstractFrameDecorator.php(895): Dompdf\FrameReflower\Page->reflow(NULL)
#21 /var/www/bookstack/vendor/dompdf/dompdf/src/Dompdf.php(847): Dompdf\FrameDecorator\AbstractFrameDecorator->reflow()
#22 /var/www/bookstack/vendor/barryvdh/laravel-dompdf/src/PDF.php(200): Dompdf\Dompdf->render()
#23 /var/www/bookstack/vendor/barryvdh/laravel-dompdf/src/PDF.php(146): Barryvdh\DomPDF\PDF->render()
#24 /var/www/bookstack/app/Entities/ExportService.php(140): Barryvdh\DomPDF\PDF->output()
#25 /var/www/bookstack/app/Entities/ExportService.php(86): BookStack\Entities\ExportService->htmlToPdf('<!doctype html>...')
#26 /var/www/bookstack/app/Http/Controllers/PageController.php(504): BookStack\Entities\ExportService->pageToPdf(Object(BookStack\Entities\Page))