Fix: Web3WebSocketProvider deinitialization crash

[andreichenchik]

Issue Description

When Web3WebSocketProvider fails to establish a connection during initialization (due to wrong URL or connectivity issues), it properly throws an error as expected. However, when the instance is later deallocated, it crashes with a fatal error:

Thread 1: Fatal error: Unexpectedly found nil while implicitly unwrapping an Optional value

This occurs because:

1. The webSocket property is declared as an implicitly unwrapped optional (WebSocket!)
2. If initialization fails before webSocket is assigned, it remains nil
3. During deinitialization, the code unconditionally attempts to access this nil value

Fix

Added a nil check before attempting to close the WebSocket connection:

deinit {
    closed = true
    
    // Close connection if already initialized
    if let webSocket {
        _ = webSocket.close(code: .goingAway)
    }

    // As described in https://github.com/apple/swift-nio/issues/2371
    try? wsEventLoopGroup.syncShutdownGracefully()
}

This change ensures the Web3WebSocketProvider can be safely deallocated even when a connection couldn't be established, improving error handling and preventing crashes during cleanup.