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.

1 files changed, 3 insertions, 0 deletions

diff --git a/st.c b/st.c
index e55e7b3..6f40e35 100644
--- a/st.c
+++ b/st.c
@@ -965,6 +965,9 @@ tsetdirt(int top, int bot)
 {
         int i;
 
+        if (term.row <= 0)
+                return;
+
         LIMIT(top, 0, term.row-1);
         LIMIT(bot, 0, term.row-1);