Error: Call to a member function getThirdPartySetting() on null

Problem/motivation

When attempting to move a block within Layout Builder for a dashboard entity provided by the Dashboard module → , a fatal error occurs because the dashboard entity does not utilise an Entity View Display. Layout Builder Restrictions expects a valid view display to be available. Since dashboards do not define or use view modes or view displays by default, the method blockAllowedinContext() receives a NULL value, causing a fatal error:

Error: Call to a member function getThirdPartySetting() on null in EntityViewModeRestriction->blockAllowedinContext()

This makes it impossible to move blocks in the dashboard layout when Layout Builder Restrictions is enabled.

Steps to reproduce

1. Enable the dashboard, layout_builder, and layout_builder_restrictions modules.
2. Create a new dashboard.
3. Go to the layout builder UI for the created dashboard.
4. Try to move an existing block.
5. Observe that a fatal error is thrown and the layout breaks.

Proposed resolution

Add a null check inside EntityViewModeRestriction::blockAllowedinContext() to skip restrictions if no view display is available.