let user select one of the folders data/, sdata/

closes #133 (closed)

sohstationviewer/model/mseed_data/mseed.py

@@ -129,6 +129,10 @@ class MSeed(GeneralData):
                    "Please select one to display")
             self.pause_signal.emit(msg, sta_ids)
             self.pause()
+            if self.pause_response == -1:
+                self.track_info('Process is cancelled by user.',
+                                LogType.WARNING)
+                return
             selected_sta_id = sta_ids[self.pause_response]
 
         self.track_info(f'Select Station {selected_sta_id}', LogType.INFO)