Stop pagination when root event received

Riot/Modules/MatrixKit/Models/Room/MXKRoomDataSource.m

@@ -1448,6 +1448,16 @@ typedef NS_ENUM (NSUInteger, MXKRoomDataSourceError) {
             return NO;
         }
     }
+
+    if (!USE_THREAD_TIMELINE && direction == MXTimelineDirectionBackwards && self.threadId)
+    {
+        //  when not using a thread timeline, data source will desperately fill the screen  with events by filtering them locally.
+        //  we can stop when we see the thread root event when paginating backwards
+        if ([event.eventId isEqualToString:self.threadId])
+        {
+            self.shouldStopBackPagination = YES;
+        }
+    }
     
     return YES;
 }