Research tweaks

core/src/mindustry/game/Team.java

@@ -9,6 +9,7 @@ import mindustry.game.Rules.*;
 import mindustry.game.Teams.*;
 import mindustry.graphics.*;
 import mindustry.world.blocks.storage.CoreBlock.*;
+import mindustry.world.modules.*;
 
 import static mindustry.Vars.*;
 
@@ -71,6 +72,12 @@ public class Team implements Comparable<Team>{
         hasPalette = true;
     }
 
+    /** @return the core items for this team, or an empty item module.
+     * Never add to the resulting item module, as it is mutable. */
+    public @NonNull ItemModule items(){
+        return core() == null ? ItemModule.empty : core().items;
+    }
+
     /** @return the team-specific rules. */
     public TeamRule rules(){
         return state.rules.teams.get(this);