add error log for unsupported charset

Author: wxiaoguang

modules/charset/charset.go

@@ -9,6 +9,7 @@ import (
 	"strings"
 	"unicode/utf8"
 
+	"code.gitea.io/gitea/modules/log"
 	"code.gitea.io/gitea/modules/setting"
 	"code.gitea.io/gitea/modules/util"
 
@@ -74,7 +75,8 @@ func ToUTF8(content []byte, opts ConvertOpts) []byte {
 
 	encoding, _ := charset.Lookup(charsetLabel)
 	if encoding == nil {
-		setting.PanicInDevOrTesting("unknown detected charset %q, it shouldn't happen", charsetLabel)
+		log.Error("Unsupported detected charset %q, please check your charset setting in your config, or report an issue", charsetLabel)
+		setting.PanicInDevOrTesting("unsupported detected charset %q, it shouldn't happen", charsetLabel)
 		return content
 	}