Hello Nubuwat,
I am sorry for the delay of this reply as it is a public holiday for us here. I have checked your site and the problem seems to arise in the "System - JotCache" plugin. After disabling the JotCache plugin, the error is no longer encountered. If you try to access the URL now,
https://nubuwat.com/discuss/tags/sahih-al_bukhari.html?type=%27+convert%28varchar,0x7b5d%29+%27 , it doesn't throw any errors any longer after disabling the System - JotCache plugin.
I believe you should send this report to JotCache because looking at their codes, it looks like it's trying to run some SQL query in their system plugin based on the query string.