Enable getPastCharacterChats to work with specific character ids

public/script.js

@@ -5921,20 +5921,23 @@ export async function getChatsFromFiles(data, isGroupChat) {
  * The function sends a POST request to the server to retrieve all chats for the character. It then
  * processes the received data, sorts it by the file name, and returns the sorted data.
  *
+ * @param {null|number} [characterId=null] - When set, the function will use this character id instead of this_chid.
+ *
  * @returns {Promise<Array>} - An array containing metadata of all past chats of the character, sorted
  * in descending order by file name. Returns `undefined` if the fetch request is unsuccessful.
  */
-async function getPastCharacterChats() {
-    if (!characters[this_chid]) return;
+export async function getPastCharacterChats(characterId = null) {
+    characterId = characterId || this_chid;
+    if (!characters[characterId]) return [];
 
     const response = await fetch('/api/characters/chats', {
         method: 'POST',
-        body: JSON.stringify({ avatar_url: characters[this_chid].avatar }),
+        body: JSON.stringify({ avatar_url: characters[characterId].avatar }),
         headers: getRequestHeaders(),
     });
 
     if (!response.ok) {
-        return;
+        return [];
     }
 
     let data = await response.json();