Fix crashing in CPDFXFA_Document::GetPage()

fpdfsdk/include/fpdfxfa/fpdfxfa_page.h

Index: fpdfsdk/include/fpdfxfa/fpdfxfa_page.h
diff --git a/fpdfsdk/include/fpdfxfa/fpdfxfa_page.h b/fpdfsdk/include/fpdfxfa/fpdfxfa_page.h
index d88ba9f74585b6bb1bfc5eb1952ada7c2b8832f0..db4778470468e9c2bea48b721a0d726421b20add 100644
--- a/fpdfsdk/include/fpdfxfa/fpdfxfa_page.h
+++ b/fpdfsdk/include/fpdfxfa/fpdfxfa_page.h
@@ -20,6 +20,7 @@ class CPDFXFA_Page {
   int GetPageIndex() { return m_iPageIndex; }
   CPDF_Page* GetPDFPage() { return m_pPDFPage; }
   IXFA_PageView* GetXFAPageView() { return m_pXFAPageView; }
+  void SetXFAPageView(IXFA_PageView* pPageView) { m_pXFAPageView = pPageView; }
 
   FX_FLOAT GetPageWidth();
   FX_FLOAT GetPageHeight();