og-card: header should be hidden when neither title is nor the header slot is set

[andi-d]

Describe the bug
when neither the name property, nor the header slot is set, the space is nevertheless occupied with empty space

To Reproduce
Steps to reproduce the behavior:

1. Create an og-card instance without the name attribute or header slot
2. Open in the browser
3. See error

Expected behavior
As before, the card should not reserve space for the header.

Screenshots

Desktop (please complete the following information):

• OS: all
• Browser: all
• Version: all

Smartphone (please complete the following information):

• Device: all
• OS: all
• Browser: all
• Version all

[Cr45hCode]

Reopens: #40