Fixes error when the stacktrace is undefined

[0xR]

When a protractor test has a timeout the stacktrace value is not defined. This causes the following error output:

    some page
      ✗ should do something (0.039 secs)
        - timeout: timed out after 10 msec waiting for spec to complete

/home/0xR/workspace/node_modules/jasmine-spec-reporter/src/spec-display.js:110
    var lines = traces.split('\n');
                       ^
TypeError: Cannot call method 'split' of undefined
    at Object.SpecDisplay.filterStackTraces (/home/0xR/workspace/node_modules/jasmine-spec-reporter/src/spec-display.js:110:24)
    at Object.SpecDisplay.displayErrorMessages (/home/0xR/workspace/node_modules/jasmine-spec-reporter/src/spec-display.js:102:25)
    at Object.SpecDisplay.failed (/home/0xR/workspace/node_modules/jasmine-spec-reporter/src/spec-display.js:80:12)
    at Object.SpecReporter.reportSpecResults (/home/0xR/workspace/node_modules/jasmine-spec-reporter/src/jasmine-spec-reporter.js:85:20)

This change solves that issue.

[bcaudan]

Nice catch, thanks!
It is available in 1.1.1.