initializes field with formik value

Author: brrkrmn

Diff for: zubhub_frontend/zubhub/src/views/create_activity/script.js

@@ -520,7 +520,7 @@ export const step2Schema = {
     initialValues: {
         introduction: undefined,
         images: [],
-        materials_used: '<ol> <li></li></ol>',
+        materials_used: [],
         making_steps: [],
         materials_used_image: []
     },