Set default magnitude type to 'M' if it is 'nan' in CSV catalog

Author: claudiodsf

requake/catalog/read_catalog_from_csv.py

@@ -197,6 +197,8 @@ def read_catalog_from_csv(filename):
             ev.lat = float_or_none(row[fields['lat']])
             ev.depth = float_or_none(row[fields['depth']])
             ev.mag_type = row[fields['mag_type']]
+            if ev.mag_type.lower() == 'nan':
+                ev.mag_type = 'M'
             ev.mag = float_or_none(row[fields['mag']])
             cat.append(ev)
     print()  # needed to add a newline after the last "reading row" message