Properly close archive files after validating them

src/util.cr

@@ -95,12 +95,16 @@ 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
+  rescue e
+    file.close unless file.nil?
     e
+  end
 end
 
 def random_str