Send sticker: Fix the missing delete button on a sticker pack

https://github.com/vector-im/riot-ios/issues/1860

Riot/ViewController/RoomViewController.m

@@ -2886,7 +2886,7 @@
                                                        initForMXSession:self.roomDataSource.mxSession
                                                        inRoom:self.roomDataSource.roomId
                                                        screen:[IntegrationManagerViewController screenForWidget:kWidgetTypeStickerPicker]
-                                                       widgetId:kWidgetTypeStickerPicker];
+                                                       widgetId:nil];
 
         [self presentViewController:modularVC animated:NO completion:nil];
     }

Riot/ViewController/Widgets/StickerPickerViewController.m

@@ -52,7 +52,7 @@
                                                    initForMXSession:self.roomDataSource.mxSession
                                                    inRoom:self.roomDataSource.roomId
                                                    screen:[IntegrationManagerViewController screenForWidget:kWidgetTypeStickerPicker]
-                                                   widgetId:kWidgetTypeStickerPicker];
+                                                   widgetId:self.widget.widgetId];
 
     [self presentViewController:modularVC animated:NO completion:nil];
 }

Riot/ViewController/Widgets/WidgetViewController.h

@@ -27,6 +27,11 @@
  */
 @interface WidgetViewController : WebViewViewController
 
+/**
+ The displayed widget.
+ */
+@property (nonatomic, readonly) Widget  *widget;
+
 /**
  The room data source.
  Required if the widget needs to post messages.

Riot/ViewController/Widgets/WidgetViewController.m

@@ -21,13 +21,11 @@
 NSString *const kJavascriptSendResponseToPostMessageAPI = @"riotIOS.sendResponse('%@', %@);";
 
 @interface WidgetViewController ()
-{
-    Widget  *widget;
-}
 
 @end
 
 @implementation WidgetViewController
+@synthesize widget;
 
 - (instancetype)initWithUrl:(NSString*)widgetUrl forWidget:(Widget*)theWidget
 {