Bump to 688f70a. st: guard tsetdirt() against zero-sized terminal

tsetdirt() assumes term.row > 0. During early init or
resize paths this may not hold, leading to out-of-bounds
access. Bail out early if there are no rows.

https://git.suckless.org/st/commit/688f70add0d1da8a416bf7df763328d694a24a3a.html

st.c

@@ -1102,6 +1102,9 @@ tsetdirt(int top, int bot)
 {
 	int i;
 
+	if (term.row <= 0)
+		return;
+
 	LIMIT(top, 0, term.row-1);
 	LIMIT(bot, 0, term.row-1);