not all files have trodes version

Author: zm711

neo/rawio/spikegadgetsrawio.py

@@ -124,8 +124,6 @@ def _parse_header(self):
         hconf = root.find("HardwareConfiguration")
         sconf = root.find("SpikeConfiguration")
 
-        # store trode version in case there are version changes in the future
-        self._trode_version = gconf.attrib["trodesVersion"]
         self._sampling_rate = float(hconf.attrib["samplingRate"])
         num_ephy_channels = int(hconf.attrib["numChannels"])