Respect ToUnicode map when it maps a charcode to unicode 0

core/fpdftext/cpdf_textpage.cpp

Index: core/fpdftext/cpdf_textpage.cpp
diff --git a/core/fpdftext/cpdf_textpage.cpp b/core/fpdftext/cpdf_textpage.cpp
index c691d4b3a0706370c50a45bcd5897f711e1c7f90..105694329221539426e00d15e1be6c98e48f9f0c 100644
--- a/core/fpdftext/cpdf_textpage.cpp
+++ b/core/fpdftext/cpdf_textpage.cpp
@@ -1131,12 +1131,8 @@ void CPDF_TextPage::ProcessTextObject(PDFTEXT_Obj Obj) {
     spacing = 0;
     CFX_WideString wstrItem = pFont->UnicodeFromCharCode(item.m_CharCode);
     bool bNoUnicode = false;
-    FX_WCHAR wChar = wstrItem.GetAt(0);
-    if ((wstrItem.IsEmpty() || wChar == 0) && item.m_CharCode) {
-      if (wstrItem.IsEmpty())
-        wstrItem += (FX_WCHAR)item.m_CharCode;
-      else
-        wstrItem.SetAt(0, (FX_WCHAR)item.m_CharCode);
+    if (wstrItem.IsEmpty() && item.m_CharCode) {
+      wstrItem += static_cast<FX_WCHAR>(item.m_CharCode);
       bNoUnicode = true;
     }
     charinfo.m_Index = -1;