Remove "this==NULL" and adjust corresponding callers

core/src/fpdfdoc/doc_annot.cpp

Index: core/src/fpdfdoc/doc_annot.cpp
diff --git a/core/src/fpdfdoc/doc_annot.cpp b/core/src/fpdfdoc/doc_annot.cpp
index 227578a974ffbe035668fd86a4b499487d6cf66c..89528455701f41f510b95c180ed4aaaffa5a364a 100644
--- a/core/src/fpdfdoc/doc_annot.cpp
+++ b/core/src/fpdfdoc/doc_annot.cpp
@@ -165,7 +165,7 @@ void CPDF_Annot::ClearCachedAP()
 }
 CFX_ByteString CPDF_Annot::GetSubType() const
 {
-    return m_pAnnotDict->GetConstString(FX_BSTRC("Subtype"));
+    return m_pAnnotDict ? m_pAnnotDict->GetConstString(FX_BSTRC("Subtype")) : CFX_ByteStringC();
 }
 void CPDF_Annot::GetRect(CPDF_Rect& rect) const
 {
@@ -202,7 +202,8 @@ CPDF_Stream* FPDFDOC_GetAnnotAP(CPDF_Dictionary* pAnnotDict, CPDF_Annot::Appeara
         if (as.IsEmpty()) {
             CFX_ByteString value = pAnnotDict->GetString(FX_BSTRC("V"));
             if (value.IsEmpty()) {
-                value = pAnnotDict->GetDict(FX_BSTRC("Parent"))->GetString(FX_BSTRC("V"));
+                CPDF_Dictionary* pDict = pAnnotDict->GetDict(FX_BSTRC("Parent"));
+                value = pDict ? pDict->GetString(FX_BSTRC("V")) : CFX_ByteString();
             }
             if (value.IsEmpty() || !((CPDF_Dictionary*)psub)->KeyExist(value)) {
                 as = FX_BSTRC("Off");