Fixed mission onBegin() being called many times

core/src/io/anuke/mindustry/core/Logic.java

@@ -112,6 +112,7 @@ public class Logic extends Module{
             world.getSector().completedMissions ++;
 
             state.mode = world.getSector().currentMission().getMode();
+            world.getSector().currentMission().onFirstBegin();
             world.getSector().currentMission().onBegin();
             world.sectors.save();
         }

core/src/io/anuke/mindustry/maps/TutorialSector.java

@@ -99,7 +99,7 @@ public class TutorialSector{
             },
             new BattleMission(){
                 public void generate(Generation gen){} //no
-                public void onBegin(){} //also no
+                public void onFirstBegin(){} //also no
             }.setMessage("$tutorial.battle")
         );
 

core/src/io/anuke/mindustry/maps/missions/BattleMission.java

@@ -25,7 +25,7 @@ public class BattleMission extends Mission{
     }
 
     @Override
-    public void onBegin(){
+    public void onFirstBegin(){
         if(state.teams.get(defaultTeam).cores.size == 0){
             return;
         }

core/src/io/anuke/mindustry/maps/missions/ExpandMission.java

@@ -25,7 +25,7 @@ public class ExpandMission extends ActionMission{
     }
 
     @Override
-    public void onBegin(){
+    public void onFirstBegin(){
         runner.run();
     }
 

core/src/io/anuke/mindustry/maps/missions/Mission.java

@@ -62,6 +62,10 @@ public abstract class Mission{
 
     }
 
+    public void onFirstBegin(){
+
+    }
+
     /**Shows the unique sector message.*/
     public void showMessage(){
         if(!headless && extraMessage != null){