Possible access of undefined variable

[svenvarkel]

In webapp.js there is a possible access of undefined variable. It needs a check if it's defined, first.

2016-05-06T10:59:13.042Z - error: TypeError: Cannot read property 'raw_node' of undefined
    at Object.onCommit (...node_modules/strider-bitbucket/lib/webapp.js:297:49)

[svenvarkel]

This issue relates to #17 because it all starts when the commit list is empty. However better checks for undef variables should be added anyway.

[knownasilya]

@svenvarkel PR is very welcome