fix(webdav): set mime by ext if it's empty

pkg/utils/file.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"io"
 	"io/ioutil"
+	"mime"
 	"os"
 	"path"
 	"path/filepath"
@@ -136,3 +137,12 @@ func GetFileType(filename string) int {
 	}
 	return conf.UNKNOWN
 }
+
+func GetMimeType(name string) string {
+	ext := path.Ext(name)
+	m := mime.TypeByExtension(ext)
+	if m != "" {
+		return m
+	}
+	return "application/octet-stream"
+}