Comment 1 for bug 101767

Those 'handles' or controls in the tables never worked. AFAIK, anyway.
Did you use them in earlier Silva versions?

They're unique to Mozilla/Firefox, and since they're browser specific,
Kupu doesn't have code that hooks into them. The only way to adjust
tables is in the table toolbox. Changing, say the width or height of
the table by dragging doesn't work either.

It's really unfortunate that attempting to use the add controls messes
up the document, although I'm having trouble reproducing the error
(but I'm not doubting that it occurred :-))