fix bug in index_first_element

pyatsoleiloutils/readmatfile.py

@@ -34,7 +34,7 @@ def readmomapmat(
     s_indexes=f['momap']['s_indexes'][0,0][:,0]
     s_array=f['momap']['s_array'][0,0][:,0]
     nturns=f['momap']['nturns'][0,0][:,0]
-    index_first_element = f['momap']['index_first_element'][:]
+    index_first_element = f['momap']['index_first_element'][0,0][:,0]
 
     return momap_pn, s_indexes, s_array, index_first_element