I tried searching for this
<?= to understand more about it, but unfortunately, the page results looks like this:
Which is NOT what the 0 results looks like normally. Therefore, I think it's a bug.
More info: Tested in Google Chrome without extensions and in Firefox with Adblock Plus, both of them in Ubuntu. Other result pages are display normally, even the 0 results pages.
P.S. I hope this is not already posted, but, as you can understand from the nature of this, I was not able to search if this bug was already here. Google didn't find me any result either.
Edit after the fix, for the nature of the bug I can see how this yield to so many duplicates in the past: