FPDF_PageDelete must delete XFA pages as well.

fpdfsdk/fpdfeditpage.cpp

Index: fpdfsdk/fpdfeditpage.cpp
diff --git a/fpdfsdk/fpdfeditpage.cpp b/fpdfsdk/fpdfeditpage.cpp
index e10f3825afcce3fc30dc2679204e72be2899f20d..493329c3604b27edfb40522f33fee40a6a647113 100644
--- a/fpdfsdk/fpdfeditpage.cpp
+++ b/fpdfsdk/fpdfeditpage.cpp
@@ -57,11 +57,8 @@ DLLEXPORT FPDF_DOCUMENT STDCALL FPDF_CreateNewDocument() {
 }
 
 DLLEXPORT void STDCALL FPDFPage_Delete(FPDF_DOCUMENT document, int page_index) {
-  CPDF_Document* pDoc = CPDFDocumentFromFPDFDocument(document);
-  if (!pDoc || page_index < 0 || page_index >= pDoc->GetPageCount())
-    return;
-
-  pDoc->DeletePage(page_index);
+  if (UnderlyingDocumentType* pDoc = UnderlyingFromFPDFDocument(document))
+    pDoc->DeletePage(page_index);
 }
 
 DLLEXPORT FPDF_PAGE STDCALL FPDFPage_New(FPDF_DOCUMENT document,