fix(scripts): correct bash-3.2 comment's stated mechanism in bump-objectui.sh (#12306)

The bash-3.2 note explaining why the ref-collection loop uses `if [[ -n "$x" ]]; then …; fi`
rather than a trailing `[[ … ]] && …` attributed the trap to the empty-list case. Measured
on bash 5.2.21, that does not reproduce: an all-empty read leaves the loop body unexecuted
and the `while` exits 0. The real trap is a non-empty read whose last line fails the test,
and only once that loop is the last command of a function — the `&&`-list's false status
becomes the loop's exit status, becomes the function's return, and `set -e` kills the
caller on that. Measured over all four combinations (empty vs. non-empty-with-failing-last-
line × loop-is-fn's-last-command vs. not): only that one combination exits 1; the other
three exit 0.

The `if` form itself is unchanged and correct — only the stated reason was wrong.

Fixes #12222


Claude-Session: https://claude.ai/code/session_af22b339-91b5-5814-8b9b-2453fc5b3f68

Co-authored-by: Claude <noreply@anthropic.com>

Author: yinlianghui

scripts/bump-objectui.sh

@@ -339,8 +339,15 @@ report_objectui_reachability() {
   # (`enable -n mapfile readarray` via `BASH_ENV`) plus a static scan.
   # Keep this loop bash-3.2-clean: no `mapfile`, no `readarray`, no
   # `declare -A`, no `${x^^}`/`${x,,}`. The `if` (rather than `[[ … ]] &&`) is
-  # load-bearing under `set -e`: a trailing false `&&`-list would make the
-  # whole `while` return 1 and kill the run on an empty ref list.
+  # load-bearing under `set -e` — but NOT on an empty ref list: an all-empty
+  # read leaves the loop body unexecuted and the `while` exits 0 either way
+  # (measured, bash 5.2.21). The real trap is a NON-EMPTY read whose LAST
+  # line fails the `[[ -n … ]]` test, and only once that loop is the LAST
+  # command of a function: the `&&`-list's false status becomes the loop's
+  # exit status, which becomes the function's return, which `set -e` then
+  # kills the caller on. Measured over all four combinations (empty vs.
+  # non-empty-with-failing-last-line × loop-is-fn's-last-command vs. not):
+  # only that one combination dies (exit 1); the other three exit 0.
   local -a local_refs=() remote_refs=()
   local ref_line=''
   while IFS= read -r ref_line; do