Show an activity indicator until the preview has loaded.

Riot/Modules/Room/CellData/RoomBubbleCellData.h

@@ -82,10 +82,15 @@ typedef NS_ENUM(NSInteger, RoomBubbleCellDataTag)
 @property(nonatomic, readonly) CGFloat additionalContentHeight;
 
 /**
- A link if the textMessage contains one, otherwise nil.
+ The data necessary to show a URL preview.
  */
 @property (nonatomic) URLPreviewData *urlPreviewData;
 
+/**
+ Whether a URL preview should be displayed for this cell.
+ */
+@property (nonatomic) BOOL showURLPreview;
+
 /**
  MXKeyVerification object associated to key verification event when using key verification by direct message.
  */

Riot/Modules/Room/CellData/RoomBubbleCellData.m

@@ -1070,8 +1070,9 @@ NSString *const URLPreviewDidUpdateNotification = @"URLPreviewDidUpdateNotificat
         return;
     }
     
-    // Check that the preview hasn't been dismissed already.
-    if ([URLPreviewManager.shared hasClosedPreviewFrom:lastComponent.event])
+    // Don't show the preview if it has been dismissed already.
+    self.showURLPreview = ![URLPreviewManager.shared hasClosedPreviewFrom:lastComponent.event];
+    if (!self.showURLPreview)
     {
         return;
     }