default not found image

app/controllers/blobs_controller.rb

@@ -10,11 +10,12 @@ class BlobsController < ApplicationController
   end
 
   def contents
+    thumb = params[:thumb]
+    raise("invalid thumb #{thumb}") if !thumb.blank? && !thumb_params(thumb)
+
     expires_dur = 1.year
     response.headers["Expires"] = expires_dur.from_now.httpdate
     expires_in expires_dur, public: true
-    thumb = params[:thumb]
-    raise("invalid thumb #{thumb}") if !thumb.blank? && !thumb_params(thumb)
 
     sha256 = params[:id]
     etag = sha256

app/helpers/domain/fa/users_helper.rb

@@ -9,6 +9,9 @@ module Domain::Fa::UsersHelper
     elsif (path = user.avatar&.guess_file_uri_from_hles)
       path
     end
+  rescue
+    # default / 'not found' avatar image
+    "/blobs/9080fd4e7e23920eb2dccfe2d86903fc3e748eebb2e5aa8c657bbf6f3d941cdc/contents.jpg"
   end
 
   def sanitized_fa_user_profile_html(html)