Use correct default language when no Accept-Language is set

Closes #792

Signed-off-by: Thomas Citharel <tcit@tcit.fr>

lib/web/plugs/set_locale_plug.ex

@@ -9,19 +9,20 @@ defmodule Mobilizon.Web.Plugs.SetLocalePlug do
   Plug to set locale for Gettext
   """
   import Plug.Conn, only: [get_req_header: 2, assign: 3]
+  alias Mobilizon.Web.Gettext, as: GettextBackend
 
   def init(_), do: nil
 
   def call(conn, _) do
-    locale = get_locale_from_header(conn) || Gettext.get_locale()
-    Gettext.put_locale(locale)
+    locale = get_locale_from_header(conn)
+    GettextBackend.put_locale(locale)
     assign(conn, :locale, locale)
   end
 
   defp get_locale_from_header(conn) do
     conn
     |> extract_accept_language()
-    |> Enum.find(&supported_locale?/1)
+    |> Enum.find("", &supported_locale?/1)
   end
 
   defp extract_accept_language(conn) do
@@ -41,7 +42,7 @@ defmodule Mobilizon.Web.Plugs.SetLocalePlug do
   end
 
   defp supported_locale?(locale) do
-    Mobilizon.Web.Gettext
+    GettextBackend
     |> Gettext.known_locales()
     |> Enum.member?(locale)
   end