Width/height fallback where value is 0 and description in formatter

Problem/Motivation

The width and height has a fallback on empty values. But a value of 0 should also be handled as 100% and saved as empty.
Also the formatter should display the fallback behavior.

Steps to reproduce

Enter 0 as value for width and height
See that the video uses the 0 values instead of 100%
The description in the formatter displays empty and 0 values

Proposed resolution

Do not save 0 values but make them empty.
Show the correct description in the formatter.

Remaining tasks

Create a patch

User interface changes

Correct display of description in formatter.

API changes

None.

Data model changes

None.