Fix crash.

pdf/pdfium/pdfium_engine.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 "pdf/pdfium/pdfium_engine.h"
 
 #include <math.h>
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 2578 matching lines @@
     CheckPageAvailable(FPDFAvail_GetFirstPageNum(doc_), &pending_pages_);
   }
 
   LoadPageInfo(false);
 
   if (doc_loader_->IsDocumentComplete())
     FinishLoadingDocument();
 }
 
 void PDFiumEngine::LoadPageInfo(bool reload) {
+  if (!doc_loader_)
+    return;
   pending_pages_.clear();
   pp::Size old_document_size = document_size_;
   document_size_ = pp::Size();
   std::vector<pp::Rect> page_rects;
   int page_count = FPDF_GetPageCount(doc_);
   bool doc_complete = doc_loader_->IsDocumentComplete();
   bool is_linear = FPDFAvail_IsLinearized(fpdf_availability_) == PDF_LINEARIZED;
   for (int i = 0; i < page_count; ++i) {
     if (i != 0) {
       // Add space for horizontal separator.
@@ skipping 1414 matching lines @@
   FPDF_DOCUMENT doc =
       FPDF_LoadMemDocument(pdf_buffer, pdf_buffer_size, nullptr);
   if (!doc)
     return false;
   bool success = FPDF_GetPageSizeByIndex(doc, page_number, width, height) != 0;
   FPDF_CloseDocument(doc);
   return success;
 }
 
 }  // namespace chrome_pdf