DList bug or programmer error?

[Daniel K]

This block of code fails the second assert, why? Using 
stableRemove{Front,Back} does not fix it.

----
import std.range;
import std.container;
unittest {
  auto dl2 = DList!int([2,7]);
  dl2.removeFront();
  //dl2.stableRemoveFront();
  assert(dl2[].walkLength == 1);
  dl2.removeBack();
  //dl2.stableRemoveBack();
  assert(dl2.empty, "not empty?!");
}


void main(){
}
----

rdmd -unittest file.d