Fix#32684, regression of #32596 (side-effect of jQuery removal: jQuery could tolerate non-existing elements)
And fix another regression bug from #30453 (initCompReactionSelector double-init)
None of the frontend js/ts files was touched besides these two commands
(edit: no longer true, I touched one file in
61105d0618
because of a deprecation that was not showing before the rename).
`tsc` currently reports 778 errors, so I have disabled it in CI as
planned.
Everything appears to work fine.
