TypeError: Cannot read property 'text' of undefined

I'm facing 1 issue on my Unit Test. It happens when I tried to add `babelify` into `browerify`'s transform to convert ES6 in my implement code.

```
browserify: {
transform: ['babelify', 'reactify', 'istanbulify'],
extensions: ['.js', '.jsx'],
debug: true,
bundleDelay: 1000, // WAR for karma-browserify race condition
},
```

I'm using:
- Istanbul: `0.3.17`
- karma-coverage: `0.4.2`
- babelify: `6.1.2`

Chrome 43.0.2357 (Mac OS X 10.10.2): Executed 313 of 324 (skipped 11) SUCCESS (0.515 secs / 0.313 secs)

ERROR [coverage]: [TypeError: Cannot read property 'text' of undefined]
TypeError: Cannot read property 'text' of undefined
at /node_modules/istanbul/lib/report/html.js:283:53
at Array.forEach (native)
at annotateBranches (/node_modules/istanbul/lib/report/html.js:250:30)
at HtmlReport.Report.mix.writeDetailPage (/node_modules/istanbul/lib/report/html.js:421:9)
at /node_modules/istanbul/lib/report/html.js:484:26
at SyncFileWriter.extend.writeFile (/node_modules/istanbul/lib/util/file-writer.js:57:9)
at FileWriter.extend.writeFile (/node_modules/istanbul/lib/util/file-writer.js:147:23)
at /node_modules/istanbul/lib/report/html.js:483:24
at Array.forEach (native)
at HtmlReport.Report.mix.writeFiles (/node_modules/istanbul/lib/report/html.js:477:23)

Reproduce the failure with the shown browserify transforms and package versions, then inspect node_modules/istanbul/lib/report/html.js around annotateBranches at lines 250-283 and the karma-coverage integration. Done means the existing unit-test run completes without the TypeError and produces an HTML coverage report.

Written by the indexing model from the issue text.