ZODB Components: Fix startup of old Sites not having portal_components yet.

In such case, it must obviously be considered that the ZODB Component Document
was not found and thus fallback on filesystem Document.

2018-11-21 17:05:01,919 WARNING ERP5Type.Dynamic Could not access Portal Type Object for type 'Category Tool'
Traceback (most recent call last):
  File "product/ERP5Type/dynamic/lazy_class.py", line 3
52, in loadClass
    class_definition = generatePortalTypeClass(site, portal_type)
  File "product/ERP5Type/dynamic/portal_type_class.py",
 line 198, in generatePortalTypeClass
    module = erp5.component.document.find_load_module(type_class)
  File "product/ERP5Type/dynamic/component_package.py",
 line 361, in find_load_module
    loader = self.find_module(fullname)
  File "product/ERP5Type/dynamic/component_package.py",
 line 155, in find_module
    component_tool = aq_base(site.portal_components)
AttributeError: portal_components

product/ERP5Type/dynamic/component_package.py

@@ -136,7 +136,13 @@ class ComponentDynamicPackage(ModuleType):
         id_ = "%s.%s.%s" % (self._id_prefix, version, name)
         # aq_base() because this should not go up to ERP5Site and trigger
         # side-effects, after all this only check for existence...
-        component = getattr(aq_base(site.portal_components), id_, None)
+        try:
+          component_tool = aq_base(site.portal_components)
+        except AttributeError:
+          # For old sites, just use FS Documents...
+          return None
+
+        component = getattr(component_tool, id_, None)
         if component is None or component.getValidationState() not in ('modified',
                                                                        'validated'):
           return None
@@ -152,7 +158,12 @@ class ComponentDynamicPackage(ModuleType):
 
       # name=REFERENCE
       else:
-        component_tool = aq_base(site.portal_components)
+        try:
+          component_tool = aq_base(site.portal_components)
+        except AttributeError:
+          # For old sites, just use FS Documents...
+          return None
+
         for version in site.getVersionPriorityNameList():
           id_ = "%s.%s.%s" % (self._id_prefix, version, name)
           component = getattr(component_tool, id_, None)