Unable to publish add if Available is not selected initially

[ghost]

Steps to reproduce:

• go to https://am-ui.azurewebsites.net or open the local docker environment on https://localhost:4200
• click on Create an add
• select Accommodation
• don't select anything on the Available dropdown and fill everything else(date selection for availability will be disabled)
• click on Preview and publish - Available dropdown and the date field on the right should be marked as invalid
• select a value for Available and a date next to the dropdown

Expected behavior:

• Preview and publish button should be enabled

Currently:

• Preview and publish button is disabled and the Available dropdown stays marked as invalid