0.5.18 fix next \ prev doc

DocsApp/models.py

@@ -71,12 +71,15 @@ class DocArt(BaseModelViewPage):
         if not version:
             version = self.get_last_version()
 
-        art = DocArt.objects.filter(
-            enable=True,
-            versions=version,
-            order__lt=self.order,
-            parent=self.parent
-        ).order_by('-order').first()
+        kwargs = {
+            'enable': True,
+            'versions': version,
+            'parent': self.parent
+        }
+        if self.order:
+            kwargs['order__lt'] = self.order
+
+        art = DocArt.objects.filter(**kwargs).order_by('-order').first()
 
         if art:
             while art.get_last_child(version=version):
@@ -94,12 +97,16 @@ class DocArt(BaseModelViewPage):
 
         art = self.get_first_child(version=version)
         if not art:
-            art = DocArt.objects.filter(
-                enable=True,
-                versions=version,
-                order__gt=self.order,
-                parent=self.parent
-            ).order_by('order').first()
+
+            kwargs = {
+                'enable': True,
+                'versions': version,
+                'parent': self.parent
+            }
+            if self.order:
+                kwargs['order__gt'] = self.order
+
+            art = DocArt.objects.filter(**kwargs).order_by('order').first()
 
         if not art and self.parent:
             art = DocArt.objects.filter(