[Bug] Tabs widget broken on mobile/fluid width

## Description

On a mobile device, the Tabs widget can't be switched, since the tabbar is missing. Also, the content inside the tabs is cut off.

### Steps to reproduce the behaviour:
1. Create a new project
2. Switch to Fluid Width
3. Drag a Tabs widget into the canvas (Optionally add a text widget to one of the tabs and enter some static text)
4. Deploy the page
5. Open on mobile (I tried iOS 14.2 Safari)
6. Tabs can't be switched (controls are not visible). Tab content is cut off. Might be related to #3415.

### Important Details
- Version: Cloud
- OS: Edited on Windows, viewed on iOS 14.2
- Browser: Chrome 89