In the review summary dialog, there is now an "open an issue" checkbox after each comment.
Also fixed the way we get checkbox states in reviews.js

Tested in my local linux machine with Chrome using the following steps
1. take any review request, view its diffs
2. comment on any line of the diff, open an issue
3. comment on some other line of the diff, don't open an issue
4. there should be a green bar on top, click the "edit review" button
5. in the summary, uncheck the "open an issue" in the first comment, don't modify the comment content
6. check the "open an issue" in the second comment, don't modify the comment content
7. save the review
8. refresh the page, and see that the issue states have been changed accordingly