Fix NULL crash in PrintViewManager::PrintPreviewDone.

chrome/browser/printing/print_preview_dialog_controller.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/printing/print_preview_dialog_controller.h"
 
 #include <stddef.h>
 
 #include <algorithm>
 #include <string>
@@ skipping 148 matching lines @@
 }
 
 // static
 void PrintPreviewDialogController::PrintPreview(WebContents* initiator) {
   if (initiator->ShowingInterstitialPage() || initiator->IsCrashed())
     return;
 
   PrintPreviewDialogController* dialog_controller = GetInstance();
   if (!dialog_controller)
     return;
-  if (!dialog_controller->GetOrCreatePreviewDialog(initiator))
-    PrintViewManager::FromWebContents(initiator)->PrintPreviewDone();
+  if (!dialog_controller->GetOrCreatePreviewDialog(initiator)) {
+    PrintViewManager* print_view_manager =
+        PrintViewManager::FromWebContents(initiator);
+    if (print_view_manager)
+      print_view_manager->PrintPreviewDone();
+  }
 }
 
 WebContents* PrintPreviewDialogController::GetOrCreatePreviewDialog(
     WebContents* initiator) {
   DCHECK(initiator);
 
   // Get the print preview dialog for |initiator|.
   WebContents* preview_dialog = GetPrintPreviewForContents(initiator);
   if (preview_dialog) {
     // Show the initiator holding the existing preview dialog.
@@ skipping 309 matching lines @@
         static_cast<PrintPreviewUI*>(web_ui->GetController());
     if (print_preview_ui)
       print_preview_ui->OnPrintPreviewDialogDestroyed();
   }
 
   preview_dialog_map_.erase(preview_dialog);
   RemoveObservers(preview_dialog);
 }
 
 }  // namespace printing