[Bug] When Metamask extension is not installed, "Log in with Ethereum" button throws an uncaught exception in the console

[blei-schmetterling]

Not sure why exactly it cannot fetch ETH accounts, but it doesn't fall gracefully: the button appear dead.

Here's what happens in the console:

And here's the JS file it complains about:

Steps to reproduce:

• [ ] open a clean browser (Firefox, Chrome, Safari, anything goes)
• [ ] visit https://projects.ethberlin.org/teams and
• [ ] observe the outcome

[blei-schmetterling]

To bypass the issue you need to install https://metamask.io, this part is obvious. The problem is to correctly handle the case when the extension is not there: I'd probably redirect to metamask webpage in this case.