Fixed building post refmaps

boards/models/post/__init__.py

@@ -147,7 +147,7 b' class Post(models.Model, Viewable):'
     def get_absolute_url(self, thread=None):
         # Url is cached only for the "main" thread. When getting url
         # for other threads, do it manually.
-        return self.url
+        return self.url or self._build_url()
 
     def get_thread(self):
         return self.thread
@@ -268,13 +268,14 b' class Post(models.Model, Viewable):'
                                                 include_last_update)
 
     def _build_url(self):
-        opening = self.is_opening()
-        opening_id = self.id if opening else self.get_thread().get_opening_post_id()
-        url = reverse('thread', kwargs={'post_id': opening_id})
-        if not opening:
-            url += '#' + str(self.id)
+        if self.id:
+            opening = self.is_opening()
+            opening_id = self.id if opening else self.get_thread().get_opening_post_id()
+            url = reverse('thread', kwargs={'post_id': opening_id})
+            if not opening:
+                url += '#' + str(self.id)
 
-        return url
+            return url
 
     def save(self, force_insert=False, force_update=False, using=None,
              update_fields=None):
@@ -293,7 +294,8 b' class Post(models.Model, Viewable):'
         super().save(force_insert, force_update, using, update_fields)
 
         if new_post:
-            self.url = self._build_url()
+            if not self.url:
+                self.url = self._build_url()
             super().save(update_fields=['url'])
 
     def get_text(self) -> str: