Call CheckLinearizedFirstPage() when loading the first linearized page.

core/src/fpdfapi/fpdf_parser/fpdf_parser_parser.cpp

Index: core/src/fpdfapi/fpdf_parser/fpdf_parser_parser.cpp
diff --git a/core/src/fpdfapi/fpdf_parser/fpdf_parser_parser.cpp b/core/src/fpdfapi/fpdf_parser/fpdf_parser_parser.cpp
index 2a271f11793d869e94e8b21166f71f1070ba7a41..05f407bfd3a8158c10c0319f79cfad4878f1487b 100644
--- a/core/src/fpdfapi/fpdf_parser/fpdf_parser_parser.cpp
+++ b/core/src/fpdfapi/fpdf_parser/fpdf_parser_parser.cpp
@@ -4381,6 +4381,8 @@ int CPDF_DataAvail::IsPageAvail(int32_t iPage, IFX_DownloadHints* pHints) {
 
   if (m_bLinearized) {
     if ((FX_DWORD)iPage == m_dwFirstPageNo) {
+      if (!CheckLinearizedFirstPage(iPage, pHints))
+        return DataNotAvailable;
       m_pagesLoadState.insert(iPage);
       return DataAvailable;
     }