Fix NexradWorker crash when minute key is missing from args

Jobs enqueued via backfill only have year/month/day/hour — default
minute to 0 instead of requiring it in the pattern match.

lib/microwaveprop/workers/nexrad_worker.ex

@@ -27,7 +27,8 @@ defmodule Microwaveprop.Workers.NexradWorker do
 
   @impl Oban.Worker
   def perform(%Oban.Job{args: args}) do
-    %{"year" => year, "month" => month, "day" => day, "hour" => hour, "minute" => minute} = args
+    %{"year" => year, "month" => month, "day" => day, "hour" => hour} = args
+    minute = Map.get(args, "minute", 0)
     {:ok, date} = Date.new(year, month, day)
     {:ok, time} = Time.new(hour, minute, 0)
     {:ok, timestamp} = DateTime.new(date, time, "Etc/UTC")