Update SQLFORM deleted = False if readonly

fixes the following syntax:

form = SQLFORM(table, record, readonly=readonly, deletable=True)

form.process()

if form.deleted:
   pass
elif form.accepted:
   pass

gluon/sqlhtml.py

@@ -1676,6 +1676,7 @@ class SQLFORM(FORM):
             keepvalues = True if self.record else False
 
         if self.readonly:
+            self.deleted = False
             return False
 
         if request_vars.__class__.__name__ == 'Request':