Fix null crash in CheckTrailer.

core/src/fpdfapi/fpdf_parser/fpdf_parser_parser.cpp

Index: core/src/fpdfapi/fpdf_parser/fpdf_parser_parser.cpp
diff --git a/core/src/fpdfapi/fpdf_parser/fpdf_parser_parser.cpp b/core/src/fpdfapi/fpdf_parser/fpdf_parser_parser.cpp
index 08cc9e5b51dfad5b85ba1fe97d3b50f8afed2985..f043d13f0a8ff08a8b724434168b5dc00f7d63dc 100644
--- a/core/src/fpdfapi/fpdf_parser/fpdf_parser_parser.cpp
+++ b/core/src/fpdfapi/fpdf_parser/fpdf_parser_parser.cpp
@@ -3828,14 +3828,14 @@ FX_BOOL CPDF_DataAvail::CheckTrailer(IFX_DownloadHints* pHints)
         CFX_SmartPointer<IFX_FileStream> file(FX_CreateMemoryStream(pBuf, (size_t)iSize, FALSE));
         m_syntaxParser.InitParser((IFX_FileStream*)file, 0);
         CPDF_Object *pTrailer = m_syntaxParser.GetObject(NULL, 0, 0, 0);
-        if (pTrailer->GetType() != PDFOBJ_DICTIONARY) {
-            return FALSE;
-        }
         if (!pTrailer) {
             m_Pos += m_syntaxParser.SavePos();
             pHints->AddSegment(m_Pos, iTrailerSize);
             return FALSE;
         }
+        if (pTrailer->GetType() != PDFOBJ_DICTIONARY) {
+            return FALSE;
+        }
         CPDF_Dictionary *pTrailerDict = pTrailer->GetDict();
         if (pTrailerDict) {
             CPDF_Object *pEncrypt = pTrailerDict->GetElement("Encrypt");