Fix assert in conversation view around nil title.

// FREEBIE

Signal/src/ViewControllers/ConversationView/MessagesViewController.m

@@ -457,6 +457,7 @@ typedef enum : NSUInteger {
 
     [self initializeToolbars];
     [self createScrollDownButton];
+    [self createHeaderViews];
 }
 
 - (void)registerCustomMessageNibs
@@ -545,8 +546,6 @@ typedef enum : NSUInteger {
     // or on another device.
     [self hideInputIfNeeded];
 
-    [self setNavigationTitle];
-
     self.isViewVisible = YES;
 
     // restart any animations that were stopped e.g. while inspecting the contact info screens.
@@ -1033,14 +1032,10 @@ typedef enum : NSUInteger {
     [self setBarButtonItemsForDisappearingMessagesConfiguration:configuration];
 }
 
-- (void)setBarButtonItemsForDisappearingMessagesConfiguration:
+- (void)createHeaderViews
-    (OWSDisappearingMessagesConfiguration *)disappearingMessagesConfiguration
 {
-    UIBarButtonItem *backItem = [self createOWSBackButton];
-    const CGFloat unreadCountViewDiameter = 16;
-    if (_backButtonUnreadCountView == nil) {
     _backButtonUnreadCountView = [UIView new];
-        _backButtonUnreadCountView.layer.cornerRadius = unreadCountViewDiameter / 2;
+    _backButtonUnreadCountView.layer.cornerRadius = self.unreadCountViewDiameter / 2;
     _backButtonUnreadCountView.backgroundColor = [UIColor redColor];
     _backButtonUnreadCountView.hidden = YES;
     _backButtonUnreadCountView.userInteractionEnabled = NO;
@@ -1050,32 +1045,7 @@ typedef enum : NSUInteger {
     _backButtonUnreadCountLabel.textColor = [UIColor whiteColor];
     _backButtonUnreadCountLabel.font = [UIFont systemFontOfSize:11];
     _backButtonUnreadCountLabel.textAlignment = NSTextAlignmentCenter;
-    }
-    // This method gets called multiple times, so it's important we re-layout the unread badge
-    // with respect to the new backItem.
-    [backItem.customView addSubview:_backButtonUnreadCountView];
-    // TODO: The back button assets are assymetrical.  There are strong reasons
-    // to use spacing in the assets to manipulate the size and positioning of
-    // bar button items, but it means we'll probably need separate RTL and LTR
-    // flavors of these assets.
-    [_backButtonUnreadCountView autoPinEdgeToSuperviewEdge:ALEdgeTop withInset:-6];
-    [_backButtonUnreadCountView autoPinLeadingToSuperViewWithMargin:1];
-    [_backButtonUnreadCountView autoSetDimension:ALDimensionHeight toSize:unreadCountViewDiameter];
-    // We set a min width, but we will also pin to our subview label, so we can grow to accommodate multiple digits.
-    [_backButtonUnreadCountView autoSetDimension:ALDimensionWidth
-                                          toSize:unreadCountViewDiameter
-                                        relation:NSLayoutRelationGreaterThanOrEqual];
-
-    [_backButtonUnreadCountView addSubview:_backButtonUnreadCountLabel];
-    [_backButtonUnreadCountLabel autoPinWidthToSuperviewWithMargin:4];
-    [_backButtonUnreadCountLabel autoPinHeightToSuperview];
 
-    // Initialize newly created unread count badge to accurately reflect the current unread count.
-    [self updateBackButtonUnreadCount];
-
-
-    const CGFloat kTitleVSpacing = 0.f;
-    if (!self.navigationBarTitleView) {
     self.navigationBarTitleView = [UIView containerView];
     [self.navigationBarTitleView
         addGestureRecognizer:[[UITapGestureRecognizer alloc] initWithTarget:self
@@ -1095,8 +1065,40 @@ typedef enum : NSUInteger {
     self.navigationBarSubtitleLabel = [UILabel new];
     [self updateNavigationBarSubtitleLabel];
     [self.navigationBarTitleView addSubview:self.navigationBarSubtitleLabel];
-    }
+}
 
+- (CGFloat)unreadCountViewDiameter
+{
+    return 16;
+}
+
+- (void)setBarButtonItemsForDisappearingMessagesConfiguration:
+    (OWSDisappearingMessagesConfiguration *)disappearingMessagesConfiguration
+{
+    UIBarButtonItem *backItem = [self createOWSBackButton];
+    // This method gets called multiple times, so it's important we re-layout the unread badge
+    // with respect to the new backItem.
+    [backItem.customView addSubview:_backButtonUnreadCountView];
+    // TODO: The back button assets are assymetrical.  There are strong reasons
+    // to use spacing in the assets to manipulate the size and positioning of
+    // bar button items, but it means we'll probably need separate RTL and LTR
+    // flavors of these assets.
+    [_backButtonUnreadCountView autoPinEdgeToSuperviewEdge:ALEdgeTop withInset:-6];
+    [_backButtonUnreadCountView autoPinLeadingToSuperViewWithMargin:1];
+    [_backButtonUnreadCountView autoSetDimension:ALDimensionHeight toSize:self.unreadCountViewDiameter];
+    // We set a min width, but we will also pin to our subview label, so we can grow to accommodate multiple digits.
+    [_backButtonUnreadCountView autoSetDimension:ALDimensionWidth
+                                          toSize:self.unreadCountViewDiameter
+                                        relation:NSLayoutRelationGreaterThanOrEqual];
+
+    [_backButtonUnreadCountView addSubview:_backButtonUnreadCountLabel];
+    [_backButtonUnreadCountLabel autoPinWidthToSuperviewWithMargin:4];
+    [_backButtonUnreadCountLabel autoPinHeightToSuperview];
+
+    // Initialize newly created unread count badge to accurately reflect the current unread count.
+    [self updateBackButtonUnreadCount];
+
+    const CGFloat kTitleVSpacing = 0.f;
     // We need to manually resize and position the title views;
     // iOS AutoLayout doesn't work inside navigation bar items.
     [self.navigationBarTitleLabel sizeToFit];