ODK Build Error with rake db:migrate

Hi everyone,

I'm completely new to Ruby and ODK and I try to install ODK Build (OS: Windows 10). I successfully ran bundle install, but when I run the command "bundle exec rake db:migrate", there is a following error:

** Invoke db:migrate (first_time)
** Execute db:migrate
rake aborted!
NoMethodError: undefined method []' for nil:NilClass C:/Users/elly1/Documents/Uni/Hiwi-Job/ODK-Build/build/server/model/connection_manager.rb:26:in open_connections_if_necessary!'
C:/Users/elly1/Documents/Uni/Hiwi-Job/ODK-Build/build/server/model/connection_manager.rb:15:in call' C:/Users/elly1/Documents/Uni/Hiwi-Job/ODK-Build/build/server/model/connection_manager.rb:49:in rackless_connection'
C:/Users/elly1/Documents/Uni/Hiwi-Job/ODK-Build/build/Rakefile:49:in block (2 levels) in <top (required)>' C:/Ruby26-x64/lib/ruby/gems/2.6.0/gems/rake-13.0.1/lib/rake/task.rb:281:in block in execute'
C:/Ruby26-x64/lib/ruby/gems/2.6.0/gems/rake-13.0.1/lib/rake/task.rb:281:in each' C:/Ruby26-x64/lib/ruby/gems/2.6.0/gems/rake-13.0.1/lib/rake/task.rb:281:in execute'
C:/Ruby26-x64/lib/ruby/gems/2.6.0/gems/rake-13.0.1/lib/rake/task.rb:219:in block in invoke_with_call_chain' C:/Ruby26-x64/lib/ruby/2.6.0/monitor.rb:235:in mon_synchronize'
C:/Ruby26-x64/lib/ruby/gems/2.6.0/gems/rake-13.0.1/lib/rake/task.rb:199:in invoke_with_call_chain' C:/Ruby26-x64/lib/ruby/gems/2.6.0/gems/rake-13.0.1/lib/rake/task.rb:188:in invoke'
C:/Ruby26-x64/lib/ruby/gems/2.6.0/gems/rake-13.0.1/lib/rake/application.rb:160:in invoke_task' C:/Ruby26-x64/lib/ruby/gems/2.6.0/gems/rake-13.0.1/lib/rake/application.rb:116:in block (2 levels) in top_level'
C:/Ruby26-x64/lib/ruby/gems/2.6.0/gems/rake-13.0.1/lib/rake/application.rb:116:in each' C:/Ruby26-x64/lib/ruby/gems/2.6.0/gems/rake-13.0.1/lib/rake/application.rb:116:in block in top_level'
C:/Ruby26-x64/lib/ruby/gems/2.6.0/gems/rake-13.0.1/lib/rake/application.rb:125:in run_with_threads' C:/Ruby26-x64/lib/ruby/gems/2.6.0/gems/rake-13.0.1/lib/rake/application.rb:110:in top_level'
C:/Ruby26-x64/lib/ruby/gems/2.6.0/gems/rake-13.0.1/lib/rake/application.rb:83:in block in run' C:/Ruby26-x64/lib/ruby/gems/2.6.0/gems/rake-13.0.1/lib/rake/application.rb:186:in standard_exception_handling'
C:/Ruby26-x64/lib/ruby/gems/2.6.0/gems/rake-13.0.1/lib/rake/application.rb:80:in run' C:/Ruby26-x64/lib/ruby/gems/2.6.0/gems/rake-13.0.1/exe/rake:27:in <top (required)>'
C:/Ruby26-x64/bin/rake:23:in load' C:/Ruby26-x64/bin/rake:23:in '
Tasks: TOP => db:migrate
Error closing Postgres connection. Some minor data loss may have occurred for in-flight transactions.

My config.yml file:

version: 2.0
jobs:
build:
docker:
- image: circleci/ruby:2.3.3
working_directory: ~/work
steps:
- checkout
- restore_cache:
key: v1-gems-{{ checksum "Gemfile.lock" }}
- run:
name: Install dependencies
command: |
sudo apt-get update
sudo apt-get install -y zlib1g-dev libbz2-dev default-jre
- run:
name: Install and deploy
command: |
cp config.yml.sample config.yml
bundle install --path vendor/bundle
bundle exec rake deploy:build
echo $CIRCLE_SHA1 > .build_rev
tar jcf build.tar.bz2 * .build_rev .build_time
- store_artifacts:
path: /home/circleci/work/build.tar.bz2
- save_cache:
key: v1-gems-{{ checksum "Gemfile.lock" }}
paths:
- /home/circleci/work/vendor/bundle
notify:
webhooks:
- url: "http://staging.build.opendatakit.org:5566/deploy"
experimental:
notify:
branches:
only:
- "staging"

workflows:
version: 2
build:
jobs:
- build

development:
cookie_secret: sample
cookie_ssl_only: false
database:
host: localhost
database: odkbuild
user: odkbuild
password: odkbuild

test:
cookie_secret: sample

staging:
cookie_secret: sample

production:
cookie_secret: sample
google_analytics_id: UA-12345678-9

Does anyone have some idea?

Regards,

Elena