Fix NULL crash in PrintViewManager::PrintPreviewDone.

chrome/browser/printing/print_preview_dialog_controller.cc

Index: chrome/browser/printing/print_preview_dialog_controller.cc
diff --git a/chrome/browser/printing/print_preview_dialog_controller.cc b/chrome/browser/printing/print_preview_dialog_controller.cc
index bdd814fa8eb686554acecfe5a679370f73c7254f..7179c34916cbcfa03c5e5927100dab0a43a7c7ff 100644
--- a/chrome/browser/printing/print_preview_dialog_controller.cc
+++ b/chrome/browser/printing/print_preview_dialog_controller.cc
@@ -166,8 +166,12 @@ void PrintPreviewDialogController::PrintPreview(WebContents* initiator) {
   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(