Empty screen appears after tapping the "Add a processing filter" button

[strepkovaas]

Env: OS is Sisyphus-KWorkstation-10.1-x86-64 with KDE Frameworks 5.107.0

Product Version: Mayavi-4.8.1

Steps to reproduce:

1. Launch Mayavi
2. Add Data Source -> Create a parametric surface source -> Add module or filter -> Choose any sample.
3. Colors and legends -> Add a processing filter

Observed result: Empty screen appears after tapping the "Add a processing filter" button

Expected result: Should this button be disabled?