Tabler icons not displaying properly

[csalvato]

Duplicate of #103 but in English.

The icons work in edit mode but do not render in viewing mode.

Reproduction steps:

1. Install and set the Dev theme as active
2. Install the tabler picker plugin
3. While editing, pick a tabler icon using the tabler picker to be rendered in the the block
4. Click away from the block

Expected Behavior: The icon renders

Actual Behavior: An unattractive dummy character renders instead.

How can we help getting tabler icon support?