present from signalsViewController so users don't get confused by being

dropped into a different thread when the call is over.

e.g. chatting with Alice, but Bob calls. When I end the call with Bob It
would be too easy to fire off a message assuming it's going to Bob.

// FREEBIE

Signal/src/Signal-Bridging-Header.h

@@ -22,6 +22,7 @@
 #import "PropertyListPreferences.h"
 #import "PushManager.h"
 #import "SettingsTableViewController.h"
+#import "SignalsViewController.h"
 #import "UIColor+OWS.h"
 #import "UIFont+OWS.h"
 #import "UIUtil.h"

Signal/src/call/UserInterface/CallUIAdapter.swift

@@ -40,9 +40,9 @@ extension CallUIAdaptee {
         callViewController.thread = thread
         callViewController.modalTransitionStyle = .crossDissolve
 
-        guard let presentingViewController = UIApplication.shared.frontmostViewController else {
-            Logger.error("in \(#function) frontmost view controller unexpectedly nil")
-            assertionFailure("in \(#function) frontmost view controller unexpectedly nil")
+        guard let presentingViewController = Environment.getCurrent().signalsViewController else {
+            Logger.error("in \(#function) view controller unexpectedly nil")
+            assertionFailure("in \(#function) view controller unexpectedly nil")
             return
         }