do not try to convert to string a None float value

outils/views.py

@@ -204,7 +204,7 @@ class ExportPOS(View):
                         # p['name'] is a sequence generated string
                         # Test order is important as CHEQDEJ contains CHEQ for ex.
                         # p['journal'] could be used but easier to change in Odoo interface
-                        sub_amount = round(float(p['total_amount']), 2)
+                        sub_amount = round(float(p['total_amount']), 2) if p['total_amount'] else 0.00
                         if 'CSH' in p['name']:
                             csh = sub_amount
                         elif 'CHEQDEJ' in  p['name']:
@@ -317,7 +317,7 @@ class ExportPOS(View):
 
         totals = {}
         for r in res:
-            if (float(r['total_amount']) > 0):
+            if r['total_amount'] and float(r['total_amount']) > 0:
                 # d = time.strptime(r['min_date'], tf)
                 # date = str(d.tm_mday) + '-' + str(d.tm_mon) + '-' + str(d.tm_year)
                 date, hours = r['min_date'].split(' ')