Crash when starting bot without any requestData in startBotParams

[eugenDrobov]

In function
private func fetchStartBot<T: Decodable>(startBotParams: APIRequest) async throws -> T {
we have these lines
`if let customBodyParams = startBotParams.requestData {
request.httpBody = try JSONEncoder().encode(startBotParams.requestData)
}

        Logger.shared.debug(
            "Fetching from \(String(data: request.httpBody!, encoding: .utf8) ?? "")"
        )`

and if request.httpBody is nil - String(data: request.httpBody!, produces a crash