Fixes Patreon login screen not appearing on iOS 13

AltStore/Patreon/PatreonAPI.swift

@@ -71,7 +71,7 @@ extension PatreonAPI
     }
 }
 
-class PatreonAPI
+class PatreonAPI: NSObject
 {
     static let shared = PatreonAPI()
     
@@ -84,8 +84,9 @@ class PatreonAPI
     private let session = URLSession(configuration: .ephemeral)
     private let baseURL = URL(string: "https://www.patreon.com/")!
     
-    private init()
+    private override init()
     {
+        super.init()
     }
 }
 
@@ -129,6 +130,11 @@ extension PatreonAPI
             }
         }
         
+        if #available(iOS 13.0, *)
+        {
+            self.authenticationSession?.presentationContextProvider = self
+        }
+        
         self.authenticationSession?.start()
     }
     
@@ -384,3 +390,12 @@ private extension PatreonAPI
         task.resume()
     }
 }
+
+@available(iOS 13.0, *)
+extension PatreonAPI: ASWebAuthenticationPresentationContextProviding
+{
+    func presentationAnchor(for session: ASWebAuthenticationSession) -> ASPresentationAnchor
+    {
+        return UIApplication.shared.keyWindow ?? UIWindow()
+    }
+}