I am doing some custom JS work to rearrange a particular page and am running into a case where it breaks the Tabledrag functionality due to a failure to have some defensive coding (it assumes a result for cell[0] and breaks if it doesn't exist).

Uncaught TypeError: can't access property "colSpan", cell[0] is undefined

This issue seems also to have been reported in modern Drupal as well.

I don't have STR because my use is atypical -- but I propose some minor defensive coding, taken from the patch offered in that Drupal queue, to prevent the JS from crashing in edge cases like mine.