Test case for removing and adding system with same priority causess infinite loop

SystemTests.as

		[Test]
		public function removeSystemAndAddItAgainDontCauseInvalidLinkedList():void {
			var systemB:System = new System();
			var systemC:System = new System();
			game.addSystem( systemB, 0 );
			game.addSystem( systemC, 0 );
			game.removeSystem(systemB);
			game.addSystem(systemB, 0);
//			game.update( 0.1 );
			assertThat( systemC.previous, nullValue() );
			assertThat( systemB.next, nullValue() );
		}