rake db:create db:migrate fails with rake aborted! NoMethodError: undefined method `+' for nil:NilClass

When I try to do rake db:create db:migrate it fails with rake aborted! NoMethodError: undefined method `+' for nil:NilClass

Whats the issue here?

    $ rake db:create db:migrate --trace
rake aborted!
NoMethodError: undefined method `+' for nil:NilClass
/Users/Anna/Downloads/myapp/lib/firebase_url.rb:7:in `<class:FirebaseURL>'
/Users/Anna/Downloads/myapp/lib/firebase_url.rb:3:in `<top (required)>'
/Users/Anna/.rvm/gems/ruby-2.1.2/gems/activesupport-4.2.5/lib/active_support/dependencies.rb:274:in `require'
/Users/Anna/.rvm/gems/ruby-2.1.2/gems/activesupport-4.2.5/lib/active_support/dependencies.rb:274:in `block in require'
/Users/Anna/.rvm/gems/ruby-2.1.2/gems/activesupport-4.2.5/lib/active_support/dependencies.rb:240:in `load_dependency'
/Users/Anna/.rvm/gems/ruby-2.1.2/gems/activesupport-4.2.5/lib/active_support/dependencies.rb:274:in `require'
/Users/Anna/Downloads/myapp/config/application.rb:12:in `block in <class:Application>'
/Users/Anna/Downloads/myapp/config/application.rb:12:in `each'
/Users/Anna/Downloads/myapp/config/application.rb:12:in `<class:Application>'
/Users/Anna/Downloads/myapp/config/application.rb:10:in `<module:Honestbees>'
/Users/Anna/Downloads/myapp/config/application.rb:9:in `<top (required)>'
/Users/Anna/.rbenv/versions/2.1.2/lib/ruby/2.1.0/rubygems/core_ext/kernel_require.rb:55:in `require'
/Users/Anna/.rbenv/versions/2.1.2/lib/ruby/2.1.0/rubygems/core_ext/kernel_require.rb:55:in `require'
/Users/Anna/Downloads/myapp/Rakefile:4:in `<top (required)>'
/Users/Anna/.rvm/gems/ruby-2.1.2/gems/rake-10.5.0/lib/rake/rake_module.rb:28:in `load'
/Users/Anna/.rvm/gems/ruby-2.1.2/gems/rake-10.5.0/lib/rake/rake_module.rb:28:in `load_rakefile'
/Users/Anna/.rvm/gems/ruby-2.1.2/gems/rake-10.5.0/lib/rake/application.rb:689:in `raw_load_rakefile'
/Users/Anna/.rvm/gems/ruby-2.1.2/gems/rake-10.5.0/lib/rake/application.rb:94:in `block in load_rakefile'
/Users/Anna/.rvm/gems/ruby-2.1.2/gems/rake-10.5.0/lib/rake/application.rb:176:in `standard_exception_handling'
/Users/Anna/.rvm/gems/ruby-2.1.2/gems/rake-10.5.0/lib/rake/application.rb:93:in `load_rakefile'
/Users/Anna/.rvm/gems/ruby-2.1.2/gems/rake-10.5.0/lib/rake/application.rb:77:in `block in run'
/Users/Anna/.rvm/gems/ruby-2.1.2/gems/rake-10.5.0/lib/rake/application.rb:176:in `standard_exception_handling'
/Users/Anna/.rvm/gems/ruby-2.1.2/gems/rake-10.5.0/lib/rake/application.rb:75:in `run'
/Users/Anna/.rbenv/versions/2.1.2/bin/rake:33:in `<main>'