Fix display of prevent inheritance with no value specified

i18n/en.po

@@ -4507,6 +4507,9 @@ msgstr ""
 msgid "prevent all rules"
 msgstr ""
 
+msgid "prevent inheritance or not to be specified"
+msgstr ""
+
 #, python-brace-format
 msgid "prevent rule {0}"
 msgstr ""

i18n/fr.po

@@ -4525,6 +4525,9 @@ msgstr ""
 msgid "prevent all rules"
 msgstr "bloquer toutes les règles"
 
+msgid "prevent inheritance or not to be specified"
+msgstr "blocage de l'héritage libre"
+
 #, python-brace-format
 msgid "prevent rule {0}"
 msgstr "bloquer la règle {0}"

views/mgmt_rules.py

@@ -101,8 +101,10 @@ class RuleComplexLinkEntityAttributeView(viewlib.TextEntityAttributeView):
                 #     alternatives.append(_('XXX prevent to be specified'))
                 if prevent.prevent_inheritance:
                     alternatives.append(xml_escape(_('prevent all rules')))
-                else:
+                elif prevent.prevent_inheritance is False:
                     alternatives.append(xml_escape(_("don't prevent inheritance")))
+                else:  # unspecified
+                    alternatives.append(xml_escape(_("prevent inheritance or not to be specified")))
             non_rules = []
             for non_rule in ctrl.reverse_seda_ref_non_rule_id_from:
                 if non_rule.seda_ref_non_rule_id_to: