MailWindow: Fail silently when disposing documents

Elwig/Windows/MailWindow.xaml.cs

@@ -615,12 +615,16 @@ namespace Elwig.Windows {
         }
 
         private void DisposeDocs() {
+            try {
                 PrintDocument?.Dispose();
                 PrintDocument = null;
+            } catch { }
             if (EmailDocuments != null) {
                 foreach (var (m, docs) in EmailDocuments) {
                     foreach (var d in docs) {
+                        try {
                             d.Dispose();
+                        } catch { }
                     }
                 }
                 EmailDocuments = null;