Support assignments with a start date but without stop date

bt5/erp5_base/SkinTemplateItem/portal_skins/erp5_base/Assignment_viewFieldLibrary/my_stop_date.xml

@@ -10,8 +10,9 @@
             <key> <string>delegated_list</string> </key>
             <value>
               <list>
-                <string>title</string>
+                <string>default</string>
                 <string>description</string>
+                <string>title</string>
               </list>
             </value>
         </item>
@@ -53,6 +54,16 @@
             <key> <string>tales</string> </key>
             <value>
               <dictionary>
+                <item>
+                    <key> <string>default</string> </key>
+                    <value>
+                      <persistent> <string encoding="base64">AAAAAAAAAAI=</string> </persistent>
+                    </value>
+                </item>
+                <item>
+                    <key> <string>description</string> </key>
+                    <value> <string></string> </value>
+                </item>
                 <item>
                     <key> <string>field_id</string> </key>
                     <value> <string></string> </value>
@@ -65,6 +76,10 @@
                     <key> <string>target</string> </key>
                     <value> <string></string> </value>
                 </item>
+                <item>
+                    <key> <string>title</string> </key>
+                    <value> <string></string> </value>
+                </item>
               </dictionary>
             </value>
         </item>
@@ -72,6 +87,12 @@
             <key> <string>values</string> </key>
             <value>
               <dictionary>
+                <item>
+                    <key> <string>default</string> </key>
+                    <value>
+                      <none/>
+                    </value>
+                </item>
                 <item>
                     <key> <string>description</string> </key>
                     <value> <string>The End date of an operation</string> </value>
@@ -98,4 +119,17 @@
       </dictionary>
     </pickle>
   </record>
+  <record id="2" aka="AAAAAAAAAAI=">
+    <pickle>
+      <global name="TALESMethod" module="Products.Formulator.TALESField"/>
+    </pickle>
+    <pickle>
+      <dictionary>
+        <item>
+            <key> <string>_text</string> </key>
+            <value> <string>python: context.hasStopDate() and context.getStopDate()</string> </value>
+        </item>
+      </dictionary>
+    </pickle>
+  </record>
 </ZopeData>

product/ERP5Security/ERP5KeyAuthPlugin.py

@@ -355,7 +355,7 @@ class ERP5KeyAuthPlugin(ERP5UserManager, CookieAuthHelper):
               if assignment.getStartDate() is not None and \
                         assignment.getStartDate() > login_date:
                 continue
-              if assignment.getStopDate() is not None and \
+              if assignment.hasStopDate() and \
                   assignment.getStopDate() < login_date:
                 continue
               valid_assignment_list.append(assignment)

product/ERP5Security/ERP5UserManager.py

@@ -150,7 +150,7 @@ class ERP5UserManager(BasePlugin):
                 if assignment.getStartDate() is not None and \
                        assignment.getStartDate() > login_date:
                   continue
-                if assignment.getStopDate() is not None and \
+                if assignment.hasStopDate() and \
                        assignment.getStopDate() < login_date:
                   continue
                 valid_assignment_list.append(assignment)