Crashes on some RSS feeds

[stonetwig]

Hello,

first off, great lib and thanks for the development of this!

I have this feed http://cdn.radioplay.se/data/rss/501.xml that seems to crash when I call the get_podcast and send in the rss url.
This is the stacktrace:

Request: GET /api/rssinfo?rss=http://cdn.radioplay.se/data/rss/501.xml
** (exit) an exception was raised:
** (FunctionClauseError) no function clause matching in String.replace_trailing/3
(elixir 1.11.4) lib/string.ex:996: String.replace_trailing(nil, "/", "")
(metalove 0.3.0) lib/metalove/podcast.ex:62: Metalove.Podcast.get_by_feed_url/1
(podcloud 0.1.0) lib/podcloud_web/controllers/podcast_controller.ex:47: PodcloudWeb.PodcastController.get_podcast/1
(podcloud 0.1.0) lib/podcloud_web/controllers/podcast_controller.ex:82: PodcloudWeb.PodcastController.rss_info/2
(podcloud 0.1.0) lib/podcloud_web/controllers/podcast_controller.ex:1: PodcloudWeb.PodcastController.action/2
(podcloud 0.1.0) lib/podcloud_web/controllers/podcast_controller.ex:1: PodcloudWeb.PodcastController.phoenix_controller_pipeline/2
(phoenix 1.5.8) lib/phoenix/router.ex:352: Phoenix.Router.__call__/2
(podcloud 0.1.0) lib/podcloud_web/endpoint.ex:1: PodcloudWeb.Endpoint.plug_builder_call/2
(podcloud 0.1.0) lib/plug/debugger.ex:136: PodcloudWeb.Endpoint."call (overridable 3)"/2
(podcloud 0.1.0) lib/podcloud_web/endpoint.ex:1: PodcloudWeb.Endpoint.call/2
(phoenix 1.5.8) lib/phoenix/endpoint/cowboy2_handler.ex:65: Phoenix.Endpoint.Cowboy2Handler.init/4
(cowboy 2.8.0) e:/code/podcloud/deps/cowboy/src/cowboy_handler.erl:37: :cowboy_handler.execute/2
(cowboy 2.8.0) e:/code/podcloud/deps/cowboy/src/cowboy_stream_h.erl:300: :cowboy_stream_h.execute/3
(cowboy 2.8.0) e:/code/podcloud/deps/cowboy/src/cowboy_stream_h.erl:291: :cowboy_stream_h.request_process/3
(stdlib 3.8) proc_lib.erl:249: :proc_lib.init_p_do_apply/3

I would try to fix it myself, but I am a bit of a beginner in Elixir so I am having a bit of a trouble locating the issue exactly.