fix: don't require Redis for startup

PluralKit.Bot/Services/ShardInfoService.cs

@@ -37,6 +37,8 @@ public class ShardInfoService
 
     public async Task<IEnumerable<ShardState>> GetShards()
     {
+        if (_redis.Connection == null)
+            return new ShardState[] { };
         var db = _redis.Connection.GetDatabase();
         var redisInfo = await db.HashGetAllAsync("pluralkit:shardstatus");
         return redisInfo.Select(x => Proto.Unmarshal<ShardState>(x.Value));
@@ -48,6 +50,12 @@ public class ShardInfoService
 
         async Task Inner()
         {
+            if (_redis.Connection == null)
+            {
+                _logger.Warning("Redis is disabled, shard connection status will be unavailable.");
+                return;
+            }
+
             var db = _redis.Connection.GetDatabase();
             var redisInfo = await db.HashGetAsync("pluralkit::shardstatus", shard.ShardId);