Denial of Service in danny-avila/librechat

A vulnerability in danny-avila/librechat version git a1647d7 allows an unauthenticated attacker to cause a denial of service by sending a crafted payload to the server. The middleware `checkBan` is not surrounded by a try-catch block, and an unhandled exception will cause the server to crash. This issue is fixed in version 0.7.6.