fix: check download permission when sharing permission is enabled (#5875)

errors/errors.go

@@ -23,6 +23,7 @@ var (
 	ErrSourceIsParent           = errors.New("source is parent")
 	ErrRootUserDeletion         = errors.New("the sole admin can't be deleted")
 	ErrCurrentPasswordIncorrect = errors.New("the current password is incorrect")
+	ErrShareRequiresDownload    = errors.New("permission to share requires permission to download")
 )
 
 type ErrShortPassword struct {