Fix swipe-back-to-pop gesture.

The interactivePopGestureRecognizer machinery doesn't work when you have
a custom back button.

// FREEBIE

Signal/src/view controllers/MessagesViewController.m

@@ -462,6 +462,9 @@ typedef enum : NSUInteger {
 {
     [super viewWillAppear:animated];
 
+    // Since we're using a custom back button, we have to do some extra work to manage the interactivePopGestureRecognizer
+    self.navigationController.interactivePopGestureRecognizer.delegate = self;
+
     // We need to recheck on every appearance, since the user may have left the group in the settings VC,
     // or on another device.
     [self hideInputIfNeeded];
@@ -543,6 +546,9 @@ typedef enum : NSUInteger {
     [super viewWillDisappear:animated];
     [self toggleObservers:NO];
 
+    // Since we're using a custom back button, we have to do some extra work to manage the interactivePopGestureRecognizer
+    self.navigationController.interactivePopGestureRecognizer.delegate = nil;
+
     [_unreadContainer removeFromSuperview];
     _unreadContainer = nil;
 

Signal/src/view controllers/OWSConversationSettingsTableViewController.m

@@ -211,6 +211,10 @@ static NSString *const OWSConversationSettingsTableViewControllerSegueShowGroupM
 - (void)viewWillAppear:(BOOL)animated
 {
     [super viewWillAppear:animated];
+
+    // Since we're using a custom back button, we have to do some extra work to manage the interactivePopGestureRecognizer
+    self.navigationController.interactivePopGestureRecognizer.delegate = self;
+
     // HACK to unselect rows when swiping back
     // http://stackoverflow.com/questions/19379510/uitableviewcell-doesnt-get-deselected-when-swiping-back-quickly
     [self.tableView deselectRowAtIndexPath:[self.tableView indexPathForSelectedRow] animated:animated];
@@ -220,6 +224,9 @@ static NSString *const OWSConversationSettingsTableViewControllerSegueShowGroupM
 {
     [super viewWillDisappear:animated];
 
+    // Since we're using a custom back button, we have to do some extra work to manage the interactivePopGestureRecognizer
+    self.navigationController.interactivePopGestureRecognizer.delegate = nil;
+
     if (self.disappearingMessagesConfiguration.isNewRecord && !self.disappearingMessagesConfiguration.isEnabled) {
         // don't save defaults, else we'll unintentionally save the configuration and notify the contact.
         return;