fix: all null pointers in disconnect listeners (there was so much)

i didn't even know how the bot even functioned for the whole 5 months without me noticing

src/main/java/me/chayapak1/chomens_bot/Bot.java

@@ -387,7 +387,11 @@ public class Bot extends SessionAdapter {
         }
 
         for (final SessionListener listener : listeners) {
-            listener.disconnected(disconnectedEvent);
+            try {
+                listener.disconnected(disconnectedEvent);
+            } catch (final Exception e) {
+                logger.error(e);
+            }
         }
     }