BUGFIX: judge nil pointer stored in error interface

error.go

@@ -22,7 +22,7 @@ package zap
 
 import (
 	"sync"
-
+	"reflect"
 	"go.uber.org/zap/zapcore"
 )
 
@@ -43,7 +43,7 @@ func Error(err error) Field {
 // For the common case in which the key is simply "error", the Error function
 // is shorter and less repetitive.
 func NamedError(key string, err error) Field {
-	if err == nil {
+	if err == nil || reflect.ValueOf(err).IsNil() {
 		return Skip()
 	}
 	return Field{Key: key, Type: zapcore.ErrorType, Interface: err}