INTLY-3512: fix manifest template handling os4

[JameelB]

Motivation

The walkthrough fails to proceed from the loading page and throws the following error if the walkthrough does not have any dependencies specified in its manifest.

TypeError: Cannot read property 'metadata' of undefined (on walkthroughServices.js:119)

What

• [x] Ensure that initCustomThreadSuccess is dispatched when there's no dependencies specified in the walkthrough's manifest.
• [x] Ensure that initCustomThreadFailure is dispatched when an error occurs during the walkthrough preparation.
• [x] Bump version of the webapp to 2.19.2

NOTE: This change is specific to OpenShift 4 only

Verification Steps

1. Run the webapp locally (point to an OpenShift cluster) or update your webapp deployment to use the image quay.io/jameelb/tutorial-web-app:2.19.2
2. Ensure that walkthrough 1 is accessible
3. Ensure that walkthrough 2 is accessible

Checklist:

• [x] Code has been tested locally by PR requester
• [x] Changes have been successfully verified by another team member