Fix tb-peek-event: termbox2 returns 0 on success, not positive

ober

e1d98dd9cf1ce61aa4e46a34c51aa6df3e05f3d5

diff --git a/src/jcode/ui/tui-ffi.ss b/src/jcode/ui/tui-ffi.ss
index edfcd97..738a890 100644
--- a/src/jcode/ui/tui-ffi.ss
+++ b/src/jcode/ui/tui-ffi.ss
@@ -248,11 +248,11 @@
 
 (def (tb-poll-event)
   (let ((rc (c-tb-poll)))
-    (if (> rc 0) (read-event!) #f)))
+    (if (= rc 0) (read-event!) #f)))
 
 (def (tb-peek-event timeout-ms)
   (let ((rc (c-tb-peek timeout-ms)))
-    (if (> rc 0) (read-event!) #f)))
+    (if (= rc 0) (read-event!) #f)))
 
 (def (tui-event-key? ev)    (= (tui-event-type ev) TB_EVENT_KEY))
 (def (tui-event-resize? ev) (= (tui-event-type ev) TB_EVENT_RESIZE))