code: @Nullable
  	FluxFirstEmitting<T> ambAdditionalSource(Publisher<? extends T> source) {
  		if (array != null) {
  			int n = array.length;
  			@SuppressWarnings("unchecked") Publisher<? extends T>[] newArray =
  					new Publisher[n + 1];
  			System.arraycopy(array, 0, newArray, 0, n);
  			newArray[n] = source;
  
  			return new FluxFirstEmitting<>(newArray);
  		}
  		return null;
  	}
docs: Returns a new instance which has the additional source to be amb'd together with
  the current array of sources.
  <p>
  This operation doesn't change the current FluxFirstEmitting instance.
  
  @param source the new source to merge with the others
  
  @return the new FluxFirstEmitting instance or null if the Amb runs with an Iterable