Give a warning: "No available symbols in `Symbols` box." in figure box.

utils.py

@@ -57,6 +57,8 @@ def Kline_predict_plot(model_id, symbols, user_opinion, frequency, feature_satur
         bars = pd.DataFrame(vi)
         bars.index = bars.index.map(pd.Timestamp)
         figs.append(plot_Klines_fig(bars, codei))
+    if len(figs) < 1:
+        figs = [plot_txt('No available symbols in `Symbols` box.')]
     return ','.join(coins_not_available) if len(coins_not_available) > 0 else 'No one', figs