Error 502 on particular search

[jiru]

To Reproduce
Steps to reproduce the behavior:

1. Perform this search that includes a very long string.
2. See error 502 as "Tatoeba is currently unavailable"

Additional information
This search string came up from the server logs, probably copy-pasted from some article.

[ckjpn]

Note that the "Tatoeba is currently unavailable" error message is shown often at other times, too. The title of the page is "Tatoeba maintenance," which is usually incorrect. For me, this is often a time out error, I think. Since for complicated searches if I lower my settings to 10 sentences per page, the error message will not appear.

#1524