ReferenceError: navigator is not defined

I'm upgrading from version 2.0.2 to 2.0.5 and suddenly my test framework is failing with this:

```
ReferenceError: navigator is not defined
at .../node_modules/file-saver/src/FileSaver.js:72:60
at .../node_modules/file-saver/dist/FileSaver.min.js:1:106
at Object. (.../node_modules/file-saver/dist/FileSaver.min.js:1:154)
at Module._compile (internal/modules/cjs/loader.js:1063:30)
at Module._compile (.../node_modules/pirates/lib/index.js:99:24)
at Module._extensions..js (internal/modules/cjs/loader.js:1092:10)
at Object.newLoader [as .js] (.../node_modules/pirates/lib/index.js:104:7)
at Module.load (internal/modules/cjs/loader.js:928:32)
at Function.Module._load (internal/modules/cjs/loader.js:769:14)
at Module.require (internal/modules/cjs/loader.js:952:19)
```