Deprecate usage of nil as route path

In Rails 4 these kind of routes used to work:

```ruby
scope '/*id', controller: :builds, as: :build do
  get action: :show
end
```

But since 1a830cbd830c7f80936dff7e3c8b26f60dcc371d, routes are only created for
paths specified as strings or symbols. Implicit `nil` paths are just ignored,
with no deprecation warnings or errors. Routes are simply not created. This come
as a surprise for people migrating to Rails 5, since the lack of logs or errors
makes hard to understand where the problem is.

This commit introduces a deprecation warning in case of path as `nil`, while
still allowing the route definition.

0 files changed, 0 insertions, 0 deletions