[HttpKernel] Fixed typo

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | did not changed code
| Fixed tickets | -
| License       | MIT
| Doc PR        | -


This is just a quick patch.

But I think we have a "big" issue here. If something wrong happen during the exception handling, the last exception is hidden. Of course, the last exception is logged, But IMHO, this not very handly.

I try to isolate the bug in this simple gist https://gist.github.com/lyrixx/5570964#file-index-php .
Here the debug is a nightmare for new comers. I let you try and see ;)
IMHO, the last exception should not be hidden, but display.