Fails when targets is defined in an unconventional way

[simonihmig]

Getting TypeError: Cannot read property 'join' of undefined thrown here when targets are defined without a browsers property (example). This has worked before, I assume targets is simply passed to @babel/preset-env which does support defining targets in a variety of formats

The format I used was suggested as a workaround for a Fastboot related transpilation issue.

I just checked the original RFC, and it does mention a browsers property specifically, so I guess this is then not necessarily a bug. But maybe people have used different formats in the wild as I did, so thought I should raise this here, at least for visibility...

[ef4]

The wrinkle here is that we don't just pass this to @babel/preset-env. We also pass it to webpack's target option here.