Fix bug with some log files

Fix problem with log files that have more than one blank lines at the
end.

sohstationviewer/model/reftek_data/reftek_reader/log_file_reader.py

@@ -122,6 +122,12 @@ class LogFile:
             line = self.file.readline()
             if line == '':
                 break
+        # If there are more than one blank lines at the end of a log file, the
+        # last packet will be empty. This causes problem if the log file came
+        # from rt2ms or SOHStationViewer.
+        if not packet:
+            self.file.close()
+            raise StopIteration
         return packet
 
     def __del__(self):