slapos_pdm: workaround to prevent breaking the instance when classes are live reloaded

master/bt5/slapos_pdm/DocumentTemplateItem/portal_components/document.erp5_slapos.SoftwareProduct.py

@@ -66,6 +66,10 @@ class SoftwareProduct(ERP5SoftwareProduct):
   )
 
   def __getattribute__(self, name):
+    if SoftwareProduct is None:
+      # XXX check lazy_class to understand why the class is None sometimes...
+      # raising this error prevents breaking the instance in such case
+      raise AttributeError('SoftwareProduct class is None.')
     try:
       result = super(SoftwareProduct, self).__getattribute__(name)
     except AttributeError: