[MM-42022] Don't break importing process on missing display name of a channel (#19641)

* Don't break importing process on missing display name of a channel

* remove unused strings

Co-authored-by: = <=>

app/import_validators.go

@@ -165,9 +165,9 @@ func validateChannelImportData(data *ChannelImportData) *model.AppError {
 		return model.NewAppError("BulkImport", "app.import.validate_channel_import_data.name_characters.error", nil, "", http.StatusBadRequest)
 	}
 
-	if data.DisplayName == nil {
-		return model.NewAppError("BulkImport", "app.import.validate_channel_import_data.display_name_missing.error", nil, "", http.StatusBadRequest)
-	} else if utf8.RuneCountInString(*data.DisplayName) == 0 || utf8.RuneCountInString(*data.DisplayName) > model.ChannelDisplayNameMaxRunes {
+	if data.DisplayName == nil || utf8.RuneCountInString(*data.DisplayName) == 0 {
+		data.DisplayName = data.Name // when displayName is missing we use name instead for displaying so we might as well convert it here.
+	} else if utf8.RuneCountInString(*data.DisplayName) > model.ChannelDisplayNameMaxRunes {
 		return model.NewAppError("BulkImport", "app.import.validate_channel_import_data.display_name_length.error", nil, "", http.StatusBadRequest)
 	}