Fix null crash in CheckTrailer.

fpdfsdk/src/fpdf_dataavail_unittest.cpp

+// Copyright 2015 PDFium 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 "../../testing/embedder_test.h"
+#include "../../fpdfsdk/include/fpdfview.h"
+#include "../../fpdfsdk/include/fpdfdoc.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+class FPDFDataAvailEmbeddertest : public EmbedderTest {
+};
+
+TEST_F(FPDFDataAvailEmbeddertest, TrailerUnterminated) {
+  // Document must open without crashing but is too malformed to be available.
+  EXPECT_TRUE(OpenDocument("testing/resources/trailer_unterminated.pdf"));
+  EXPECT_FALSE(FPDFAvail_IsDocAvail(avail_, &hints_));
+}
+
+TEST_F(FPDFDataAvailEmbeddertest, TrailerAsHexstring) {
+  // Document must open without crashing but is too malformed to be available.
+  EXPECT_TRUE(OpenDocument("testing/resources/trailer_as_hexstring.pdf"));
+  EXPECT_FALSE(FPDFAvail_IsDocAvail(avail_, &hints_));
+}