even if a table has zero columns, do not segfault in the formatter;

bug reported by bentley@

1 files changed, 1 insertions, 1 deletions

diff --git a/tbl_term.c b/tbl_term.c
index 31dabe81..0ce60988 100644
--- a/tbl_term.c
+++ b/tbl_term.c
@@ -107,7 +107,7 @@ term_tbl(struct termp *tp, const struct tbl_span *sp)
 	/* Vertical frame at the start of each row. */
 
 	if ((TBL_OPT_BOX | TBL_OPT_DBOX) & sp->opts->opts ||
-	    sp->head->vert)
+	    (sp->head != NULL && sp->head->vert))
 		term_word(tp, TBL_SPAN_HORIZ == sp->pos ||
 		    TBL_SPAN_DHORIZ == sp->pos ? "+" : "|");