Revert "fix cbs"

This reverts commit 4758cd65e5fc923d1970fd17fc0dd4e5e8af7604.

helpers/avr_isp_worker.c

@@ -55,7 +55,6 @@ static const CdcCallbacks cdc_cb = {
     vcp_state_callback,
     vcp_on_cdc_control_line,
     vcp_on_line_config,
-    NULL,
 };
 
 /* VCP callbacks */