The "Branches" section is wrongly displayed as complete if a clone experiment is changed from Add-On to Pref-Flip type

[Softvision-RemusDranca]

[Affected versions]:

• Firefox Release 67.0.4 and above
• Chrome 75 and above.

[Affected Platforms]:

• All Windows
• All Mac
• All Linux

[Prerequisites]:

• You are logged in your LDAP account on the "https://stage.experimenter.nonprod.dataops.mozgcp.net/" website.
• Have an Add-On clone experiment, cloned from an complete experiment, created on Experimenter stage.

[Steps to reproduce]:

1. Open the browser with the profile from prerequisites and navigate to "https://experimenter.stage.mozaws.net/".
2. Open the experiment from prerequisites.
3. Click the "Edit" button from the "Overview" section.
4. Change the type of the experiment into a "Pref-Flip" from the "Type" section.
5. Click the "Save Draft" button and observe the "Branches" section.

[Expected result]:

• The "Branches" section is incomplete since the sections from "Firefox Pref" and "Pref Value" are not completed.

[Actual result]:

• The "Branches" section is complete even though the sections from "Firefox Pref" and "Pref Value" are not completed.

[Notes]:

• As a result, the experiment can be pushed in the "Ready to Ship" state without completing the mandatory fields from the "Firefox Pref" and "Pref Value" sections.
• Also, the sections from "Firefox Pref" and "Pref Value" are not displayed in the "Branches" section.
• Attached is a screen recording of the issue:

[shell1]

while this is an issue - if they are cloning we should not expect them to change type. It might happen - but so edge that we aren't building for that case. we can manually catch and correct those.