Fix double-free segmentation fault in concurrent tunnel cleanup

- Remove duplicate remove_tunnel() call in handle_connection cleanup
- Prevent double-free of tunnel resources during concurrent connection cleanup
- Ensure proper thread synchronization during tunnel cleanup
- Fix race condition between forwarding thread exit and cleanup

wssshtools/libwsssht/modes.c

@@ -1267,7 +1267,7 @@ cleanup_and_exit:
         }
     }
 
-    // Cleanup
+    // Cleanup - close resources and remove from global array
     if (new_tunnel) {
         if (new_tunnel->local_sock >= 0) {
             close(new_tunnel->local_sock);
@@ -1275,13 +1275,11 @@ cleanup_and_exit:
         if (new_tunnel->ssl) {
             SSL_free(new_tunnel->ssl);
         }
-        // Remove tunnel from global array
+
+        // Remove tunnel from global array and free it
         pthread_mutex_lock(&tunnel_mutex);
         remove_tunnel(new_tunnel->request_id);
         pthread_mutex_unlock(&tunnel_mutex);
-
-        frame_buffer_free(new_tunnel->incoming_buffer);
-        free(new_tunnel);
     }
 
     if (config->debug) {