Make sure erroring Missiles are killed off.

credits: clienthax

src/main/java/mekanism/defense/common/entity/EntityMissile.java

@@ -696,6 +696,7 @@ public class EntityMissile extends Entity implements IChunkLoadHandler, IExplosi
         } catch(Exception e) {
             DefenseTech.LOGGER.severe("Missile failed to explode properly. Report this to the developers.");
             e.printStackTrace();
+            setDead();
         }
     }