Fixed empty default values extra field range breaking page

Resolves #652

client/src/pages/settings/extraFieldsSettings.tsx

@@ -1,18 +1,18 @@
 import { PlusOutlined } from "@ant-design/icons";
 import { useTranslate } from "@refinedev/core";
 import {
-    Button,
-    Checkbox,
-    Flex,
-    Form,
-    FormInstance,
-    Input,
-    InputNumber,
-    Popconfirm,
-    Select,
-    Space,
-    Table,
-    message,
+  Button,
+  Checkbox,
+  Flex,
+  Form,
+  FormInstance,
+  Input,
+  InputNumber,
+  Popconfirm,
+  Select,
+  Space,
+  Table,
+  message,
 } from "antd";
 import { FormItemProps, Rule } from "antd/es/form";
 import { ColumnType } from "antd/es/table";
@@ -488,10 +488,16 @@ export function ExtraFieldsSettings() {
         } else if (Array.isArray(val) && record.field.field_type === FieldType.choice) {
           return val.join(", ");
         } else if (
-          (Array.isArray(val) && record.field.field_type === FieldType.integer_range) ||
-          record.field.field_type === FieldType.float_range
+          Array.isArray(val) && (
+            record.field.field_type === FieldType.integer_range || record.field.field_type === FieldType.float_range
+          )
         ) {
-          return `${val[0]} \u2013 ${val[1]}`;
+          let lower = val[0] ?? "";
+          let upper = val[1] ?? "";
+          if (lower === "" && upper === "") {
+            return null;
+          }
+          return `${lower} \u2013 ${upper}`;
         } else {
           return null;
         }