Fix a crash when there are zero audio buses in multichannel mode.

diff --git a/mainwindow.cpp b/mainwindow.cpp
index 313097de4de63807b5f17fa2637a31a99d2e88d0..839f1b359e1a9060fdb64a8cfdd942b0f42c26ea 100644 (file)
--- a/mainwindow.cpp
+++ b/mainwindow.cpp
@@ -956,11 +956,13 @@ void MainWindow::audio_level_callback(float level_lufs, float peak_db, vector<Au
                set_peak_label(ui->peak_display, peak_db);
 
                // NOTE: Will be invisible when using multitrack audio.
-               ui->gainstaging_knob->blockSignals(true);
-               ui->gainstaging_knob->setValue(lrintf(bus_levels[0].gain_staging_db * 10.0f));
-               ui->gainstaging_knob->blockSignals(false);
-               ui->gainstaging_db_display->setText(
-                       QString::fromStdString(format_db(bus_levels[0].gain_staging_db, DB_WITH_SIGN)));
+               if (!bus_levels.empty()) {
+                       ui->gainstaging_knob->blockSignals(true);
+                       ui->gainstaging_knob->setValue(lrintf(bus_levels[0].gain_staging_db * 10.0f));
+                       ui->gainstaging_knob->blockSignals(false);
+                       ui->gainstaging_db_display->setText(
+                               QString::fromStdString(format_db(bus_levels[0].gain_staging_db, DB_WITH_SIGN)));
+               }
 
                ui->makeup_gain_knob->blockSignals(true);
                ui->makeup_gain_knob->setValue(lrintf(final_makeup_gain_db * 10.0f));