Use correct frame list for combined

vis.py

@@ -414,7 +414,7 @@ if __name__ == '__main__':
 
     if multi_enable:
         print("Drawing combined plot...", end="")
-        for i_frame, frame in enumerate(frame_list):
+        for i_frame, frame in enumerate(multi_combined_frame_list):
             for symbol, conc_per_z in frame.items():
                 for i_z_pos, conc in enumerate(conc_per_z):
                     multi_combined_frame_list[i_frame][symbol][i_z_pos] = np.mean(conc)