fix end date field in campaign form

[MarcMichalsky]

Overview

A small typo causes the form field for the end date not to load when editing a campaign. If this is not noticed and the form is saved, the end date of the campaign is lost.

Before

• create a new campaign and set an end date
• save the campaign
• edit it again
• the end date is not displayed in the form

After

• create a new campaign and set an end date
• save the campaign
• edit it again
• the end date is displayed in the form

Comments

Technically, the parent_id is also missing in the form data (see MarcMichalsky/civicrm-core@84ef687). Even if this is intentional, it causes problems in other extensions (systopia/de.systopia.campaign#125). Should I create a separate PR for this?

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[colemanw]

Good catch Marc. This looks to be a somewhat recent regression (committed earlier this year) so can you please change the base of this PR to 5.80 and we will backport as well.
FYI @eileenmcnaughton

[MarcMichalsky]

Thanks! Rebased on 5.80.