Make overlay work with legacy bulk delete button

public/script.js

@@ -5526,6 +5526,8 @@ export async function getChatsFromFiles(data, isGroupChat) {
  * in descending order by file name. Returns `undefined` if the fetch request is unsuccessful.
  */
 async function getPastCharacterChats() {
+    if (!characters.includes(this_chid)) return;
+
     const response = await fetch("/getallchatsofcharacter", {
         method: 'POST',
         body: JSON.stringify({ avatar_url: characters[this_chid].avatar }),