Properly close archive files after validating them

src/util.cr

@@ -95,13 +95,17 @@ def compare_alphanumerically(a : String, b : String)
 end
 
 def validate_archive(path : String) : Exception?
+  file = nil
+  begin
     file = ArchiveFile.new path
     file.check
     file.close
     return
   rescue e
+    file.close unless file.nil?
     e
   end
+end
 
 def random_str
   UUID.random.to_s.gsub "-", ""