How to merge pod that contains subspec?

[sanhue0302]

i use a pod that contains subspec like AppAuth/Core, AppAuth/ExternalUserAgent
it always fail the execute pod install

MergeFile

group 'Views'
    pod 'AppAuth/Core'
end

Error

NoMethodError - undefined method `first' for nil:NilClass
/Library/Ruby/Gems/2.6.0/gems/cocoapods-pod-merge-0.0.3/lib/cocoapods-pod-merge/Main.rb:159:in `block (2 levels) in parse_mergefile'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-pod-merge-0.0.3/lib/cocoapods-pod-merge/Main.rb:137:in `each_line'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-pod-merge-0.0.3/lib/cocoapods-pod-merge/Main.rb:137:in `block in parse_mergefile'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-pod-merge-0.0.3/lib/cocoapods-pod-merge/Main.rb:134:in `open'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-pod-merge-0.0.3/lib/cocoapods-pod-merge/Main.rb:134:in `parse_mergefile'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-pod-merge-0.0.3/lib/cocoapods-pod-merge/Main.rb:48:in `begin'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-pod-merge-0.0.3/lib/cocoapods_plugin.rb:8:in `block in <module:CocoapodsPodMerge>'
/usr/local/Cellar/cocoapods/1.8.4/libexec/gems/cocoapods-1.8.4/lib/cocoapods/hooks_manager.rb:124:in `block (3 levels) in run'
/usr/local/Cellar/cocoapods/1.8.4/libexec/gems/cocoapods-1.8.4/lib/cocoapods/user_interface.rb:145:in `message'
/usr/local/Cellar/cocoapods/1.8.4/libexec/gems/cocoapods-1.8.4/lib/cocoapods/hooks_manager.rb:116:in `block (2 levels) in run'
/usr/local/Cellar/cocoapods/1.8.4/libexec/gems/cocoapods-1.8.4/lib/cocoapods/hooks_manager.rb:115:in `each'
/usr/local/Cellar/cocoapods/1.8.4/libexec/gems/cocoapods-1.8.4/lib/cocoapods/hooks_manager.rb:115:in `block in run'
/usr/local/Cellar/cocoapods/1.8.4/libexec/gems/cocoapods-1.8.4/lib/cocoapods/user_interface.rb:145:in `message'
/usr/local/Cellar/cocoapods/1.8.4/libexec/gems/cocoapods-1.8.4/lib/cocoapods/hooks_manager.rb:114:in `run'
/usr/local/Cellar/cocoapods/1.8.4/libexec/gems/cocoapods-1.8.4/lib/cocoapods/installer.rb:599:in `run_plugins_pre_install_hooks'
/usr/local/Cellar/cocoapods/1.8.4/libexec/gems/cocoapods-1.8.4/lib/cocoapods/installer.rb:219:in `block in prepare'
/usr/local/Cellar/cocoapods/1.8.4/libexec/gems/cocoapods-1.8.4/lib/cocoapods/user_interface.rb:145:in `message'
/usr/local/Cellar/cocoapods/1.8.4/libexec/gems/cocoapods-1.8.4/lib/cocoapods/installer.rb:215:in `prepare'
/usr/local/Cellar/cocoapods/1.8.4/libexec/gems/cocoapods-1.8.4/lib/cocoapods/installer.rb:155:in `install!'
/usr/local/Cellar/cocoapods/1.8.4/libexec/gems/cocoapods-1.8.4/lib/cocoapods/command/install.rb:52:in `run'
/usr/local/Cellar/cocoapods/1.8.4/libexec/gems/claide-1.0.3/lib/claide/command.rb:334:in `run'
/usr/local/Cellar/cocoapods/1.8.4/libexec/gems/cocoapods-1.8.4/lib/cocoapods/command.rb:52:in `run'
/usr/local/Cellar/cocoapods/1.8.4/libexec/gems/cocoapods-1.8.4/bin/pod:55:in `<top (required)>'
/usr/local/Cellar/cocoapods/1.8.4/libexec/bin/pod:23:in `load'
/usr/local/Cellar/cocoapods/1.8.4/libexec/bin/pod:23:in `<main>'