Address issue found in src/service-worker.js [Opened by bitHound]

 bitHound discovered 7 LintIssues in [src/service-worker.js](https://github.com/UintaGroup/blendtec-mobile/blob/212a23a0f05861b1f4f77f5c3971c8110ffdbcb1/src/service-worker.js). For details go to [bitHound](https://www.bithound.io/github/UintaGroup/blendtec-mobile/blob/212a23a0f05861b1f4f77f5c3971c8110ffdbcb1/src/service-worker.js). 