Fix build warnings.

Signal/src/ViewControllers/ConversationView/ConversationViewController.m

@@ -3750,8 +3750,9 @@ typedef enum : NSUInteger {
             lastVisibleIndexPath = indexPath;
         }
     }
-    if (lastVisibleIndexPath && lastVisibleIndexPath.row >= self.viewItems.count) {
+    if (lastVisibleIndexPath && lastVisibleIndexPath.row >= (NSInteger)self.viewItems.count) {
-        return (self.viewItems.count > 0 ? [NSIndexPath indexPathForRow:self.viewItems.count - 1 inSection:0] : nil);
+        return (self.viewItems.count > 0 ? [NSIndexPath indexPathForRow:(NSInteger)self.viewItems.count - 1 inSection:0]
+                                         : nil);
     }
     return lastVisibleIndexPath;
 }

SignalServiceKit/src/Contacts/TSThread.m

@@ -27,6 +27,8 @@ NS_ASSUME_NONNULL_BEGIN
 
 @end
 
+#pragma mark -
+
 @implementation TSThread
 
 + (NSString *)collection {

SignalServiceKit/src/Messages/DeviceSyncing/OWSOutgoingSyncMessage.m

@@ -12,6 +12,16 @@ NS_ASSUME_NONNULL_BEGIN
 
 @implementation OWSOutgoingSyncMessage
 
+- (instancetype)initWithCoder:(NSCoder *)coder
+{
+    self = [super initWithCoder:coder];
+
+    if (self) {
+    }
+
+    return self;
+}
+
 - (instancetype)init
 {
     self = [super initOutgoingMessageWithTimestamp:[NSDate ows_millisecondTimeStamp]