added mutant 2

mutants/mutant-2/swen90006/machine/Machine.java

@@ -74,7 +74,7 @@ public class Machine
   private void do_div(int dest, int src1, int src2)
   {
     if (regs[src2] == 0){
-      /* no op */
+      throw new InvalidInstructionException();
     }else{
       regs[dest] = regs[src1] / regs[src2];
     }