Remove "this==NULL" and adjust corresponding callers

core/src/fpdfapi/fpdf_parser/fpdf_parser_document.cpp

Index: core/src/fpdfapi/fpdf_parser/fpdf_parser_document.cpp
diff --git a/core/src/fpdfapi/fpdf_parser/fpdf_parser_document.cpp b/core/src/fpdfapi/fpdf_parser/fpdf_parser_document.cpp
index a4982040bf1df95a9a0cf4a2eaa89bdc3a07554b..cd100a80cc07c56f61e210855819f39904fd4578 100644
--- a/core/src/fpdfapi/fpdf_parser/fpdf_parser_document.cpp
+++ b/core/src/fpdfapi/fpdf_parser/fpdf_parser_document.cpp
@@ -61,11 +61,13 @@ void CPDF_Document::LoadAsynDoc(CPDF_Dictionary *pLinearized)
 {
     m_bLinearized = TRUE;
     m_LastObjNum = m_pParser->GetLastObjNum();
-    m_pRootDict = GetIndirectObject(m_pParser->GetRootObjNum())->GetDict();
+    CPDF_Object* indirectObj = GetIndirectObject(m_pParser->GetRootObjNum());
+    m_pRootDict = indirectObj ? indirectObj->GetDict() : NULL;
     if (m_pRootDict == NULL) {
         return;
     }
-    m_pInfoDict = GetIndirectObject(m_pParser->GetInfoObjNum())->GetDict();
+    indirectObj = GetIndirectObject(m_pParser->GetInfoObjNum());
+    m_pInfoDict = indirectObj ? indirectObj->GetDict() : NULL;
     CPDF_Array* pIDArray = m_pParser->GetIDArray();
     if (pIDArray) {
         m_ID1 = pIDArray->GetString(0);
@@ -336,7 +338,7 @@ FX_BOOL CPDF_Document::IsContentUsedElsewhere(FX_DWORD objnum, CPDF_Dictionary*
         if (pPageDict == pThisPageDict) {
             continue;
         }
-        CPDF_Object* pContents = pPageDict->GetElement(FX_BSTRC("Contents"));
+        CPDF_Object* pContents = pPageDict ? pPageDict->GetElement(FX_BSTRC("Contents")) : NULL;
         if (pContents == NULL) {
             continue;
         }