Make AttractorServer setting nil by default

App/Settings/GeneralSettingsViewController.swift

@@ -169,7 +169,7 @@ class GeneralSettingsViewController: UIViewController
                 cell.contentConfiguration = ButtonContentConfiguration(menu: menu)
             } else if identifier == Self.SyncServerItem {
                 cell.contentConfiguration = TextFieldContentConfiguration(
-                    text: Settings.shared.syncServer,
+                    text: Settings.shared.syncServer ?? "",
                     placeholderText: "https://sync.server.com",
                     textChanged: { newString in
                         Settings.shared.syncServer = newString

App/Settings/Settings.swift

@@ -107,5 +107,22 @@ class Settings
     public var userStylesheet: String = ""
     
     @SettingProperty(key: "syncServer")
-    public var syncServer: String = "https://attractor.severnaya.net"
+    public var syncServer: Optional<String> = "https://attractor.severnaya.net"
+}
+
+extension Optional: RawRepresentable where Wrapped == String
+{
+    public init?(rawValue: String?) {
+        if let rawValue {
+            self = String(rawValue: rawValue)
+        } else {
+            self = .none
+        }
+    }
+    
+    public var rawValue: String? {
+        return self
+    }
+    
+    public typealias RawValue = String?
 }

App/Sync/AttractorServer.swift

@@ -9,10 +9,20 @@ import Foundation
 
 class AttractorServer
 {
+    public enum Error: Swift.Error {
+        case missingEndpointURL
+    }
+    
     static let shared = AttractorServer()
     
-    private var endpointURL: URL {
+    private var endpointURL: URL? {
-        get { URL(string: Settings.shared.syncServer) ?? URL(string: "http://localhost")! }
+        get {
+            if let syncServer = Settings.shared.syncServer {
+                return URL(string: syncServer)
+            }
+            
+            return nil
+        }
     }
     
     private func getHostname() -> String {
@@ -21,6 +31,8 @@ class AttractorServer
     }
     
     public func publishTabInfo(_ tabInfos: [TabInfo]) {
+        guard let endpointURL else { return }
+        
         let hostName = getHostname()
         let rpcURL = endpointURL.appendingPathComponent("publishTabInfo")
         var components = URLComponents(url: rpcURL, resolvingAgainstBaseURL: false)!
@@ -44,7 +56,12 @@ class AttractorServer
         }
     }
     
-    public func getTabInfos(_ completion: @escaping(Result<[String: [TabInfo]], Error>) -> Void) {
+    public func getTabInfos(_ completion: @escaping(Result<[String: [TabInfo]], Swift.Error>) -> Void) {
+        guard let endpointURL else {
+            completion(.failure(Self.Error.missingEndpointURL))
+            return 
+        }
+        
         let rpcURL = endpointURL.appendingPathComponent("getTabInfos")
         let request = URLRequest(url: rpcURL)
         let myHostname = getHostname()