fix: add try-catch + nextMetronomeBeatRef init to startPianoRollRecording

app/static/js/app.jsx

@@ -9850,9 +9850,12 @@ const App = () => {
   };
 
   const startPianoRollRecording = (tab) => {
+    try {
       const context = getAudioContext();
       const secondsPerBeat = 60.0 / (parseInt(bpm) || 120);
       const startTime = currentTime;
+      const startBeat = startTime / secondsPerBeat;
+      nextMetronomeBeatRef.current = Math.ceil(startBeat);
       const midiRec = new ClientMIDIRecorder(context, parseInt(bpm) || 120, 4);
       midiRec.tempTabId = tab.id;
       midiRec.selectedMidiInputId = selectedMidiInputId || 'ALL';
@@ -9896,7 +9899,15 @@ const App = () => {
           s.id === tab.id ? { ...s, currentTime: startTime + sec, isDirty: true } : s
         ));
       };
+      if (!tab._recordingStarted) {
+        tab._recordingStarted = true;
+      }
       showToast('Recording MIDI to Piano Roll...', 'info');
+    } catch (err) {
+      console.error('startPianoRollRecording error:', err);
+      showToast('Lỗi khi bắt đầu ghi âm Piano Roll: ' + err.message, 'warning');
+      setRecordingState('IDLE');
+    }
   };
 
   const startRecordingTake = async (armedTracks) => {