Fluid: Removed Empty Space option for liquid domains

The option only makes sense for gas domains where there is some density.

release/scripts/startup/bl_ui/properties_physics_fluid.py

@@ -194,6 +194,7 @@ class PHYSICS_PT_settings(PhysicButtonsPanel, Panel):
                 col.prop(domain, "gravity", text="Gravity")
 
             col = flow.column()
+            if PhysicButtonsPanel.poll_gas_domain(context):
                 col.prop(domain, "clipping", text="Empty Space")
             col.prop(domain, "delete_in_obstacle", text="Delete In Obstacle")