fix(ui): handle out-of-bounds end line in code selection (#4788)

- fallback to the last line, preventing TypeError
- add E2E test

Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/4788
Reviewed-by: Gusted <gusted@noreply.codeberg.org>
Co-authored-by: Solomon Victorino <git@solomonvictorino.com>
Co-committed-by: Solomon Victorino <git@solomonvictorino.com>

web_src/js/features/repo-code.js

@@ -158,7 +158,8 @@ export function initRepoCodeView() {
       if (m) {
         $first = $linesEls.filter(`[rel=${m[1]}]`);
         if ($first.length) {
-          selectRange($linesEls, $first, $linesEls.filter(`[rel=${m[2]}]`));
+          const $last = $linesEls.filter(`[rel=${m[2]}]`);
+          selectRange($linesEls, $first, $last.length ? $last : $linesEls.last());
 
           // show code view menu marker (don't show in blame page)
           if (!isBlame()) {