Return unique_ptr<> from IPDF_StructTree

fpdfsdk/fpdf_structtree.cpp

Index: fpdfsdk/fpdf_structtree.cpp
diff --git a/fpdfsdk/fpdf_structtree.cpp b/fpdfsdk/fpdf_structtree.cpp
index 541c46b378c74561446e96a3516d7bed00c1bce1..9bc1df66f8e07738a18de5b0612a424ce51f71ab 100644
--- a/fpdfsdk/fpdf_structtree.cpp
+++ b/fpdfsdk/fpdf_structtree.cpp
@@ -25,7 +25,8 @@ DLLEXPORT FPDF_STRUCTTREE STDCALL FPDF_StructTree_GetForPage(FPDF_PAGE page) {
   CPDF_Page* pPage = CPDFPageFromFPDFPage(page);
   if (!pPage)
     return nullptr;
-  return IPDF_StructTree::LoadPage(pPage->m_pDocument, pPage->m_pFormDict);
+  return IPDF_StructTree::LoadPage(pPage->m_pDocument, pPage->m_pFormDict)
+      .release();
 }
 
 DLLEXPORT void STDCALL FPDF_StructTree_Close(FPDF_STRUCTTREE struct_tree) {