Cannot reproduce the problem with the given URL. Instead I get an error message properly displayed:
Při hledání došlo k chybě: Kvůli dočasnému problému jsme nemohli provést požadované vyhledávání. Zkuste to znovu později.
(An error has occurred while searching: We could not complete your search due to a temporary problem. Please try again later. )
For the records, XHK55ApAICkAAC9ap@kAAAAM is the execution time limit of 60 seconds was exceeded.
Yes, this is the "expected" warning and I do get it when logged out. But I can still reproduce the problem under my account.
Thanks for reminding me this information is missing: I do have PHP7 enabled.
Soooo... I tried again and managed to reproduce it. The first obstacle I found is that somehow my first try was using HHVM (according to Logstash) despite PHP7 being enabled. So I disabled and re-enabled PHP7 and tried again. This time, the search succeeded but warned me that only partial results were available. Trying for the third time finally produced the error. I can also see that sort of JSON-encoded object being echoed. At a quick glance I cannot see any private info in there, but we'd better make it disappear...
I can force the client to timeout, but I can't seem to reproduce the problem with displaying the response on screen. It seems plausible that display_errors was the problem, and is now fixed. I'm willing to call this complete and we can re-open if it is seen again.