bug when there's no waveform for a specific station id

Test case Centaur_sample: All Waveform channels checked, TPS checked, All SOH checked. Click read. Get the following error:

Dir /Users/ldam/Documents/GIT/sohstationviewer/tests/test_data/Centaur-sample can't be read due to error: Traceback (most recent call last):
  File "/Users/ldam/Documents/GIT/sohstationviewer/sohstationviewer/model/data_loader.py", line 60, in run
    data_object.__init__(
  File "/Users/ldam/Documents/GIT/sohstationviewer/sohstationviewer/model/mseed/mseed.py", line 59, in __init__
    self.read_wf_files(self.selected_key)
  File "/Users/ldam/Documents/GIT/sohstationviewer/sohstationviewer/model/mseed/mseed.py", line 282, in read_wf_files
    print('self.waveform_data[sta_id]:', self.waveform_data[sta_id])
KeyError: '3734'