Sanity check for TempoMap::get_grid ()

diff --git a/libs/ardour/tempo.cc b/libs/ardour/tempo.cc
index 42577674585e29a9f9121ff12a6a0fe19cd3e6dd..41a8f91ec563a42ff37c56f7e8c14f7dcc7c5e97 100644 (file)
--- a/libs/ardour/tempo.cc
+++ b/libs/ardour/tempo.cc
@@ -3474,7 +3474,7 @@ TempoMap::get_grid (vector<TempoMap::BBTPoint>& points,
                return;
        }
 
-       while (pos < upper) {
+       while (pos >= 0 && pos < upper) {
                pos = frame_at_beat_locked (_metrics, cnt);
                const TempoSection tempo = tempo_section_at_frame_locked (_metrics, pos);
                const MeterSection meter = meter_section_at_frame_locked (_metrics, pos);