removing a material effect from the library does not automatically remove it from the materials using the effect

[rob-bateman]

Steps to reproduce

• open blank lib
• create a new spheregeometry
• create a new mesh
• creaate a new material on the mesh
• create a new fogmethod for the material by using the plus button in the effects sub-panel
• in the materials panel on the left, select the created fog method and click the delete button
• click back on the material

Expected result

In the effects sub-panel, the fog method should have disappeared

Actual result

The fog method is still present adn applied to the material