Fix ignored writeStr return value in TiXmlDocument::SaveFile

Previously the TiXmlDocument::SaveFile could return true even when the underlying writeStr func failed.

Close #13774

PowerEditor/src/TinyXml/tinyxml.cpp

@@ -784,8 +784,7 @@ bool TiXmlDocument::SaveFile( const TCHAR * filename ) const
 		std::unique_ptr<std::string> outputStr = std::make_unique<std::string>();
 		Print(*outputStr, 0);
 		if (!outputStr->empty())
-			file.writeStr(*outputStr);
-		return true;
+			return file.writeStr(*outputStr);
 	}
 
 	return false;