Sticky Table header rows incorrectly sized if browser resized between detachments

Reproducible: always
Steps:

1. Choose a theme with a variable width layout so that sticky tables will be resized with the page
2. Open a page with at least one sticky table (i.e. /admin/modules)
3. Scroll the page far enough to trigger pinning a header table
4. Scroll back up far enough to un-pin the header table from the viewport
5. Resize the browser's width
6. Scroll back down to pin the header table again

Expected result: pinned header table matches width of content table
Actual result: pinned header table matches old width of content table before resizing

Note: the header table does live resizing properly if detached while the browser is resizing, and the lack of live updating while unpinned is good. So it just needs to reset its dimensions to its content table on (re)pinning.