Handle when server listing is unavailable

This is a bad place to display a huge error because it is a repeating
query. And also this is the first thing people see when opening the app
for the first time and it is a bad impression.

src/backend/backend.py

@@ -553,7 +553,13 @@ class Backend:
         )
 
         api_list = "https://publiclist.anchel.nl/publiclist.json"
+        try:
             response = await session.get(api_list)
+        except:
+            await session.close()
+            print("Unable to fetch", api_list)
+            return
+
         coros    = []
 
         for server in (await response.json()):