mruby/mruby — pull request #1871 by ksss (2014-03-16 14:01:38+00:00)
Title: fix bug when `0 + other object`

`0+nil` should be raise TypeError.

before
```
0+nil #=> nil
1+nil #=> TypeError
```

after
```
0+nil #=> TypeError
1+nil #=> TypeError
```

(But `if (mrb_fixnum_p(y)) {` block is never called in current situation...)