Revert "logging: Always set fields func; fix #6829"

This reverts commit 932dac157a3c4693b80576477498bb86208b9b30.

Somehow the code I was looking at changed when I committed, without realizing it. This has already been fixed in #6777.

modules/caddyhttp/logging.go

@@ -195,7 +195,6 @@ func (sa *StringArray) UnmarshalJSON(b []byte) error {
 // have richer information.
 func errLogValues(err error) (status int, msg string, fields func() []zapcore.Field) {
 	var handlerErr HandlerError
-	fields = func() []zapcore.Field { return []zapcore.Field{} } // don't be nil (fix #6829)
 	if errors.As(err, &handlerErr) {
 		status = handlerErr.StatusCode
 		if handlerErr.Err == nil {

modules/caddyhttp/server.go

@@ -408,7 +408,6 @@ func (s *Server) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 					if fields == nil {
 						fields = errFields()
 					}
-
 					c.Write(fields...)
 				}
 			}