html: default to using normal scrub policy if provided scrub policy is nil

lib/pleroma/html.ex

@@ -12,17 +12,19 @@ def get_scrubbers() do
     |> get_scrubbers
   end
 
-  def filter_tags(html, scrubber) do
-    html |> Scrubber.scrub(scrubber)
-  end
-
-  def filter_tags(html) do
+  def filter_tags(html, nil) do
     get_scrubbers()
     |> Enum.reduce(html, fn scrubber, html ->
       filter_tags(html, scrubber)
     end)
   end
 
+  def filter_tags(html, scrubber) do
+    html |> Scrubber.scrub(scrubber)
+  end
+
+  def filter_tags(html), do: filter_tags(html, nil)
+
   def strip_tags(html) do
     html |> Scrubber.scrub(Scrubber.StripTags)
   end