Added default value for mass driver bullet

core/src/mindustry/content/Blocks.java

@@ -1015,7 +1015,6 @@ public class Blocks implements ContentList{
             reloadTime = 200f;
             range = 440f;
             consumes.power(1.75f);
-            bullet = new MassDriverBolt();
         }};
 
         //special transport blocks

core/src/mindustry/world/blocks/distribution/MassDriver.java

@@ -29,7 +29,7 @@ public class MassDriver extends Block{
     public int minDistribute = 10;
     public float knockback = 4f;
     public float reloadTime = 100f;
-    public MassDriverBolt bullet;
+    public MassDriverBolt bullet = new MassDriverBolt();
     public float bulletSpeed = 5.5f;
     public float bulletLifetime = 200f;
     public Effect shootEffect = Fx.shootBig2;