Fix category search index modifying original data

Fix the category search index builder modifying the data of the original question pool for individual categories, causing them to subsequently display filtered, notably in all capital letters.

triviabot.js

@@ -1173,7 +1173,7 @@ commands.triviaPing = require("./lib/cmd_ping.js")(Config, Trivia, Database);
 commands.triviaStop = require("./lib/cmd_stop.js")(Config, Trivia, commands, getConfigVal);
 
 Trivia.buildCategorySearchIndex = async () => {
-  Trivia.categorySearchIndex = await Database.getCategories();
+  Trivia.categorySearchIndex = JSON.parse(JSON.stringify(await Database.getCategories()));
 
   for(var el in Trivia.categorySearchIndex) {
     var index = Trivia.categorySearchIndex[el];