xml: fix incorrect use of rescue

[daipom]

To surely execute return, we need brackets.
Existing implementations try to perform useless processing without return when an exception occurs.

[Watson1978]

I confirmed the YARV instruction with following 3 cases.

• 1

ruby --dump=insns -e "def hoge; return self.bar rescue nil; end"

• 2

ruby --dump=insns -e "def hoge; (return self.bar) rescue nil; end"

• 3

ruby --dump=insns -e "def hoge; return (self.bar rescue nil); end"

Then, I found 1 and 2 are same.

Here is more example.

def hoge
  if true
    return self.bar rescue nil # This should return nil as expected. However, it it not
  end

  return "hogehoge"
end

p hoge #=> hogehoge

[Watson1978]

Good catch!

[daipom]

Thanks!