raise exception for null magnitude values

src/seismic_hazard_forecasting.py

@@ -138,6 +138,12 @@ verbose: {verbose}")
 
         time, mag, lat, lon, depth = read_mat_cat(catalog_file, mag_label=mag_label, catalog_label='Catalog')
 
+        # check for null magnitude values
+        m_null_idx = np.where(np.isnan(mag))[0]
+        if len(m_null_idx) > 0:
+            msg = f"There are null values in the magnitude column of the catalog at indices {m_null_idx}"
+            logger.error(msg)
+            raise Exception(msg)
         if mc != None:
             logger.info("Mc value provided by user")
             trim_to_mc = True