Don't throw away the first frame, without making sure the second frame has a filename and linenumber.

If you're using Whoops to catch notices like "undefined variable", the second frame does not have a filename/linenumber:

![Screen Shot 2013-03-23 at 10 58 59 AM](https://f.cloud.github.com/assets/1833361/293679/9bfd43ec-93a0-11e2-9f16-80bd194d1fa3.png)

There's probably a good reason why PHP's backtrace does this, but if we throw the first away, the first item in the list can't show the matching code: 

![Screen Shot 2013-03-23 at 10 48 46 AM](https://f.cloud.github.com/assets/1833361/293680/b58f54ee-93a0-11e2-8bf8-b7bcab6607cc.png)

This patch merges `$frames[0]` and `$frames[1]`, before removing it, making sure that the first item in the list can show the matching code: 

![Screen Shot 2013-03-23 at 10 50 04 AM](https://f.cloud.github.com/assets/1833361/293682/dd915802-93a0-11e2-9b74-f05dc7b730a7.png)