Verify element exists before accessing.

core/fpdfapi/fpdf_parser/fpdf_parser_utility.cpp

Index: core/fpdfapi/fpdf_parser/fpdf_parser_utility.cpp
diff --git a/core/fpdfapi/fpdf_parser/fpdf_parser_utility.cpp b/core/fpdfapi/fpdf_parser/fpdf_parser_utility.cpp
index a738356e4384ef49b213d217ada944f72e165316..6b1958298cac3c197e54c37cbf3157d79f45e2ef 100644
--- a/core/fpdfapi/fpdf_parser/fpdf_parser_utility.cpp
+++ b/core/fpdfapi/fpdf_parser/fpdf_parser_utility.cpp
@@ -179,7 +179,7 @@ CFX_ByteTextBuf& operator<<(CFX_ByteTextBuf& buf, const CPDF_Object* pObj) {
       buf << "[";
       for (size_t i = 0; i < p->GetCount(); i++) {
         CPDF_Object* pElement = p->GetObjectAt(i);
-        if (pElement->GetObjNum()) {
+        if (pElement && pElement->GetObjNum()) {
           buf << " " << pElement->GetObjNum() << " 0 R";
         } else {
           buf << pElement;