fix an incorrect assertion that the "valid" flag is always correct in a

fix an incorrect assertion that the "valid" flag is always correct in a

2001-12-31  Havoc Pennington  <hp@pobox.com>

	* gtk/gtktextbtree.c (gtk_text_btree_node_view_check_consistency):
	fix an incorrect assertion that the "valid" flag is always correct
	in a node and add explanatory comment. This keeps me from
	reproducing #59101, but I'm remembering that 59101 was actually
	about incorrect pixel totals, so I'm not sure 59101 is actually
	fixed. May just have stopped happening due to some change in
	how C-k works.