Clean up onboarding changes.

Signal/src/environment/SignalApp.m

@@ -1,5 +1,5 @@
 //
-//  Copyright (c) 2018 Open Whisper Systems. All rights reserved.
+//  Copyright (c) 2019 Open Whisper Systems. All rights reserved.
 //
 
 #import "SignalApp.h"
@@ -166,6 +166,9 @@ NS_ASSUME_NONNULL_BEGIN
     AppDelegate *appDelegate = (AppDelegate *)[UIApplication sharedApplication].delegate;
     appDelegate.window.rootViewController = navigationController;
     OWSAssertDebug([navigationController.topViewController isKindOfClass:[HomeViewController class]]);
+
+    // Clear the signUpFlowNavigationController.
+    [self setSignUpFlowNavigationController:nil];
 }
 
 @end