2011-05-20  Andreas J. Guelzow <aguelzow@pyrshep.ca>

	* openoffice-read.c (oo_cellref_parse): return invalid_sheet when
	encountering #REF!, check for this return value in all callers
	(oo_rangeref_parse): check for invalid_sheet, check for this return
	value in all callers
	(oo_expr_rangeref_parse): check for [#REF!]

2011-05-20  Andreas J. Guelzow <aguelzow@pyrshep.ca>

	* src/sheet.h (invalid_sheet): new
	* src/sheet.c (invalid_sheet): initialize
	* src/parser.y (yylex): convs->input.range_ref might return
	invalid_sheet