Fix crash.

pdf/pdfium/pdfium_engine.cc

Index: pdf/pdfium/pdfium_engine.cc
diff --git a/pdf/pdfium/pdfium_engine.cc b/pdf/pdfium/pdfium_engine.cc
index b3386d3f3ed9e3a5292b59315595d9d11c362ab5..475d56933053765ad2f460b8ca1d7a89df84a095 100644
--- a/pdf/pdfium/pdfium_engine.cc
+++ b/pdf/pdfium/pdfium_engine.cc
@@ -2596,6 +2596,8 @@ void PDFiumEngine::ContinueLoadingDocument(const std::string& password) {
 }
 
 void PDFiumEngine::LoadPageInfo(bool reload) {
+  if (!doc_loader_)
+    return;
   pending_pages_.clear();
   pp::Size old_document_size = document_size_;
   document_size_ = pp::Size();