Added difficulty modifier for clearing sectors upon loss

core/src/mindustry/ui/dialogs/CampaignRulesDialog.java

@@ -74,6 +74,10 @@ public class CampaignRulesDialog extends BaseDialog{
                 check("@rules.rtsai.campaign", b -> rules.rtsAI = b, () -> rules.rtsAI);
             }
 
+            if(!planet.clearSectorOnLose){
+                check("@rules.clearsectoronloss", b -> rules.clearSectorOnLose = b, () -> rules.clearSectorOnLose);
+            }
+
             //TODO: this is intentionally hidden until the new mechanics have been well-tested. I don't want people immediately switching to the old mechanics
             if(planet.allowLegacyLaunchPads){
             //    check("@rules.legacylaunchpads", b -> rules.legacyLaunchPads = b, () -> rules.legacyLaunchPads);