How to instantiate item of Bundle on some condition?

[San Rise]

With Chisel 2.2.19 i can do following:

class MyBundle(withB : Boolean) extends Bundle {
  val inA = Bool(INPUT)
  val inB = if(withB) Bool(INPUT) else null
  val out = Bool(OUTPUT)
}

class MyModule extends Module {
  val io = new MyBundle(false) // OK - only on 2.2.19
  io.out := io.inA
  // val io = new MyBundle(true) // always OK
  // io.out := io.inA & io.inB
}

With such result:
//  module MyModule(input  io_inA, output io_out); //new MyBundle(false)
//    assign io_out = io_inA;
//  endmodule
// or
//  module MyModule(input  io_inA, input  io_inB, output io_out); //new MyBundle(true)
//   wire T0;
//   assign io_out = T0;
//   assign T0 = io_inA & io_inB;
//  endmodule

When I try this on Chisel > 2.2.19 i receive:
//    Exception in thread "main" java.lang.IllegalArgumentException: Flat hash tables cannot contain null elements.
...
//    at Chisel.Bundle$$anonfun$calcElements$2.apply(Bundle.scala:68)
...
//    at Chisel.Module$.Chisel$Module$$init(Module.scala:60)
//    at Chisel.Module$.apply(Module.scala:48)