Take advantage of implicit std::unique_ptr<>(nulltpr_t) ctor.

core/fpdfapi/page/cpdf_clippath.cpp

Index: core/fpdfapi/page/cpdf_clippath.cpp
diff --git a/core/fpdfapi/page/cpdf_clippath.cpp b/core/fpdfapi/page/cpdf_clippath.cpp
index 8c268a1b5e88e4e45e15a6d32206da17323fc717..9d4b737d33305942cc828e5874e7370c1c18759b 100644
--- a/core/fpdfapi/page/cpdf_clippath.cpp
+++ b/core/fpdfapi/page/cpdf_clippath.cpp
@@ -100,7 +100,7 @@ void CPDF_ClipPath::AppendTexts(
   if (pData->m_TextList.size() + pTexts->size() <= FPDF_CLIPPATH_MAX_TEXTS) {
     for (size_t i = 0; i < pTexts->size(); i++)
       pData->m_TextList.push_back(std::move((*pTexts)[i]));
-    pData->m_TextList.push_back(std::unique_ptr<CPDF_TextObject>());
+    pData->m_TextList.push_back(nullptr);
   }
   pTexts->clear();
 }