Fix a crashier in CPDFSDK_Document::GetPageView()

fpdfsdk/src/fpdfxfa/fpdfxfa_doc.cpp

Index: fpdfsdk/src/fpdfxfa/fpdfxfa_doc.cpp
diff --git a/fpdfsdk/src/fpdfxfa/fpdfxfa_doc.cpp b/fpdfsdk/src/fpdfxfa/fpdfxfa_doc.cpp
index b8549fce74b0753aecc95576f2f4b6cab094df09..36eb8370a758686a1be2f9182bba5122a50d3c72 100644
--- a/fpdfsdk/src/fpdfxfa/fpdfxfa_doc.cpp
+++ b/fpdfsdk/src/fpdfxfa/fpdfxfa_doc.cpp
@@ -45,18 +45,6 @@ CPDFXFA_Document::CPDFXFA_Document(CPDF_Document* pPDFDoc,
 }
 
 CPDFXFA_Document::~CPDFXFA_Document() {
-  if (m_pJSContext && m_pSDKDoc && m_pSDKDoc->GetEnv())
-    m_pSDKDoc->GetEnv()->GetJSRuntime()->ReleaseContext(m_pJSContext);
-
-  delete m_pSDKDoc;
-
-  if (m_pPDFDoc) {
-    CPDF_Parser* pParser = m_pPDFDoc->GetParser();
-    if (pParser)
-      delete pParser;
-    else
-      delete m_pPDFDoc;
-  }
   if (m_pXFADoc) {
     IXFA_App* pApp = m_pApp->GetXFAApp();
     if (pApp) {
@@ -66,6 +54,18 @@ CPDFXFA_Document::~CPDFXFA_Document() {
       }
     }
     delete m_pXFADoc;
+    m_pXFADoc = nullptr;

[Tom Sepez, 2016/02/03 18:02:49]

These are always worrisome; if the correct operation relies on this being null,
then some other routine (as called from the dtor) is accessing the object after
the dtor has been invoked (sometimes it's the dtor itself being re-entered).
Either way, it points out a design problem. Which is why we remove these
wherever possible, so that if we see one, we know that there's a reentrancy
issue and we must tread carefully.

Do we need this assignment and the one for m_pSDKDoc below?

+  }
+  if (m_pJSContext && m_pSDKDoc && m_pSDKDoc->GetEnv())
+    m_pSDKDoc->GetEnv()->GetJSRuntime()->ReleaseContext(m_pJSContext);
+  delete m_pSDKDoc;
+  m_pSDKDoc = nullptr;
+  if (m_pPDFDoc) {
+    CPDF_Parser* pParser = m_pPDFDoc->GetParser();
+    if (pParser)
+      delete pParser;
+    else
+      delete m_pPDFDoc;
   }
 }