fix tests

Author: kmuehlbauer

xradar/io/backends/nexrad_level2.py

@@ -634,7 +634,7 @@ def get_data_header(self):
         # get the record number from the meta header
         # message 2 is the last meta header, after which the
         # data records are located
-        if self.is_compressed:
+        if self.meta_header:
             recnum = self.meta_header["msg_2"][0]["record_number"]
         else:
             # iterate over all records to retrieve data