Fix race condition

LokiPushNotificationService/NotificationServiceExtension.swift

@@ -16,9 +16,9 @@ final class NotificationServiceExtension : UNNotificationServiceExtension {
         self.contentHandler = contentHandler
         notificationContent = (request.content.mutableCopy() as? UNMutableNotificationContent)
 
-        DispatchQueue.main.sync { self.setUpIfNecessary() }
-        
-        if let notificationContent = notificationContent {
+        DispatchQueue.main.async {
+            self.setUpIfNecessary() {
+                if let notificationContent = self.notificationContent {
                     // Modify the notification content here...
                     let base64EncodedData = notificationContent.userInfo["ENCRYPTED_DATA"] as! String
                     let data = Data(base64Encoded: base64EncodedData)!
@@ -42,6 +42,8 @@ final class NotificationServiceExtension : UNNotificationServiceExtension {
                     }
                 }
             }
+        }
+    }
     
     func handleDecryptionResult(result: OWSMessageDecryptResult, notificationContent: UNMutableNotificationContent, transaction: YapDatabaseReadWriteTransaction) {
         let contentProto = try? SSKProtoContent.parseData(result.plaintextData!)
@@ -96,7 +98,7 @@ final class NotificationServiceExtension : UNNotificationServiceExtension {
         }
     }
 
-    func setUpIfNecessary() {
+    func setUpIfNecessary(completion: @escaping () -> Void) {
         AssertIsOnMainThread()
 
         // The NSE will often re-use the same process, so if we're
@@ -132,6 +134,7 @@ final class NotificationServiceExtension : UNNotificationServiceExtension {
             },
             migrationCompletion: { [weak self] in
                 self?.versionMigrationsDidComplete()
+                completion()
             }
         )