修复全选按钮选中的问题

DownKyi/ViewModels/ViewChannelViewModel.cs

@@ -297,6 +297,7 @@ namespace DownKyi.ViewModels
             }
 
             Medias.Clear();
+            IsSelectAll = false;
             LoadingVisibility = Visibility.Visible;
             NoDataVisibility = Visibility.Collapsed;
 

DownKyi/ViewModels/ViewPublicationViewModel.cs

@@ -334,6 +334,7 @@ namespace DownKyi.ViewModels
             }
 
             Medias.Clear();
+            IsSelectAll = false;
             LoadingVisibility = Visibility.Visible;
             NoDataVisibility = Visibility.Collapsed;