Do not uselessly increment object counter.
Do not uselessly increment object counter.

	* src/object/tag.cc (block, stop): The object is always available
	through a reference, so use a reference instead of manipulating
	the object counter. Also, use "front()" instead of "[0]" to get
	the first element.

urbiforge/urbi,aldebaran/urbi,aldebaran/urbi,aldebaran/urbi,urbiforge/urbi,aldebaran/urbi,urbiforge/urbi,aldebaran/urbi,aldebaran/urbi,urbiforge/urbi,urbiforge/urbi,urbiforge/urbi,urbiforge/urbi,urbiforge/urbi,aldebaran/urbi,urbiforge/urbi,aldebaran/urbi