do nothing if configuration is skipped

config/config.exs

@@ -95,9 +95,9 @@
   ip: {0, 0, 0, 0},
   port: 9999
 
-config :pleroma, :suggestions,
-  third_party_engine:
-    "http://vinayaka.distsn.org/cgi-bin/vinayaka-user-match-suggestions-api.cgi?{{host}}+{{user}}"
+# config :pleroma, :suggestions,
+#   third_party_engine:
+#     "http://vinayaka.distsn.org/cgi-bin/vinayaka-user-match-suggestions-api.cgi?{{host}}+{{user}}"
 
 # Import environment specific config. This must remain at the bottom
 # of this file so it overrides the configuration defined above.

lib/pleroma/web/mastodon_api/mastodon_api_controller.ex

@@ -1076,13 +1076,15 @@ def errors(conn, _) do
   @suggestions Application.get_env(:pleroma, :suggestions)
 
   def suggestions(%{assigns: %{user: user}} = conn, _) do
+    api = Keyword.get(@suggestions, :third_party_engine, false)
+
+    if api do
       host =
         Application.get_env(:pleroma, Pleroma.Web.Endpoint)
         |> Keyword.get(:url)
         |> Keyword.get(:host)
 
       user = user.nickname
-    api = Keyword.get(@suggestions, :third_party_engine, "")
       url = String.replace(api, "{{host}}", host) |> String.replace("{{user}}", user)
 
       with {:ok, %{status_code: 200, body: body}} <-
@@ -1099,5 +1101,8 @@ def suggestions(%{assigns: %{user: user}} = conn, _) do
       else
         e -> Logger.error("Could not decode user at fetch #{url}, #{inspect(e)}")
       end
+    else
+      json(conn, [])
+    end
   end
 end