I've created and successfully tested custom activity type in Sitecore 9.0.0 according to this guide: https://doc.sitecore.net/developers/xp/marketing-automation/activities/activity-types/add-activity-type-to-ui.html
vendor.6be6958dbf1b66c98060.bundle.js:1 ERROR Error: Uncaught (in promise): TypeError: Cannot read property 'map' of null TypeError: Cannot read property 'map' of null at de (vendor.6be6958dbf1b66c98060.bundle.js:1) at _n (vendor.6be6958dbf1b66c98060.bundle.js:1) at l.dn (vendor.6be6958dbf1b66c98060.bundle.js:1) at View_ReadonlyEditorComponent_Host_0 (readonly-editor.component.ngfactory.ts:37)
I've also tried out a few examples from blog posts, i.e. https://www.brimit.com/blog/sitecore-marketing-automation-creating-activity-editor but none of them works on Sitecore 9.0.1, all of them fail with exact same error when I click on action and editor loads.
Has anyone managed to get custom activity type working on Sitecore 9.0.1?