Update app.py

app.py

@@ -128,9 +128,10 @@ def render_midi(input_midi, render_type, soundfont_bank, render_sample_rate, mel
             tones_chord = sorted(set([t[4] % 12 for t in c if t[3] != 9]))
             drums_events = [t for t in c if t[3] == 9]
 
-            new_tones_chord = TMIDIX.check_and_fix_tones_chord(tones_chord)
-            
-            if new_tones_chord:
+            if tones_chord:
+                
+                new_tones_chord = TMIDIX.check_and_fix_tones_chord(tones_chord)
+                
                 if len(c) > 1:
                     output_score.extend([c[0]])
                     for cc in c[1:]: