Check for non-empty string before writing to logger (fixes issue #2825)

libcef_dll/base/cef_logging.cc

@@ -256,10 +256,12 @@ ErrnoLogMessage::~ErrnoLogMessage() {
 }  // namespace cef
 
 std::ostream& operator<<(std::ostream& out, const wchar_t* wstr) {
-  cef_string_utf8_t str = {0};
   std::wstring tmp_str(wstr);
+  if (!tmp_str.empty()) {
+    cef_string_utf8_t str = {0};
     cef_string_wide_to_utf8(wstr, tmp_str.size(), &str);
     out << str.str;
     cef_string_utf8_clear(&str);
+  }
   return out;
 }