Fix: ruby#1008

I'm unfortunately unable to turn the reproduction script into
a test case there, I don't understand what is causing `err_info`
to be re-raised in the repro that doesn't work in test-unit.

```ruby
require 'json'
parser = JSON::ResumableParser.new({})
['{"message": "hello ', 'world"}', '[1,2]'].each do |chunk|
  parser << chunk
  begin
    while parser.parse
      p parser.value
    end
  rescue JSON::ParserError => e
    p e
    parser.clear
  end
end
```