[2024][ruby][6.x] tweak conditions

2024/ruby/day_06.rb

@@ -21,10 +21,13 @@ def patrol(lab)
   loop do
     pos, dir = path.last
     peek = pos.zip(dir).map {|i,di| i + di }
+
+    return path unless lab.has_key?(peek)
+
     raise Loop if seen.include?([peek, dir])
     seen << [peek, dir]
 
-    case lab.fetch(peek, nil)
+    case lab.fetch(peek)
     when ?., ?^
       path << [peek, dir]
     when ?#