change path max_length to 255 for mysql compliance

aircox/models.py

@@ -992,7 +992,7 @@ class Sound(Nameable):
         recursive = True,
         blank = True, null = True,
         unique = True,
-        max_length = 256
+        max_length = 255
     )
     embed = models.TextField(
         _('embed HTML code'),

aircox_cms/sections.py

@@ -916,7 +916,7 @@ class SectionList(BaseList, SectionRelativeItem):
 
         context.update(SectionRelativeItem.get_context(self, request, page))
         if self.url_text:
-            self.related = self.related.specific
+            self.related = self.related and self.related.specific
             target = None
             if self.related and hasattr(self.related, 'get_list_page'):
                 target = self.related.get_list_page()