运行不成功

[yangjie21]

CocoaPods' output:
↳

[!] Invalid `Podfile` file: no implicit conversion of nil into String.

 #  from /Users/sean/code/flutter/flutter-in-practice/ios/Podfile:54
 #  -------------------------------------------
 #      unless File.exist?(copied_framework_path)
 >        FileUtils.cp_r(File.join(cached_framework_dir,
 'Flutter.framework'), copied_flutter_dir)
 #      end
 #  -------------------------------------------

/Library/Ruby/Gems/2.6.0/gems/cocoapods-core-1.10.1/lib/cocoapods-core/podfi
le.rb:318:in `rescue in block in from_ruby'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-core-1.10.1/lib/cocoapods-core/podfi
le.rb:312:in `block in from_ruby'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-core-1.10.1/lib/cocoapods-core/podfi
le.rb:50:in `instance_eval'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-core-1.10.1/lib/cocoapods-core/podfi
le.rb:50:in `initialize'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-core-1.10.1/lib/cocoapods-core/podfi
le.rb:310:in `new'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-core-1.10.1/lib/cocoapods-core/podfi
le.rb:310:in `from_ruby'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-core-1.10.1/lib/cocoapods-core/podfi
le.rb:276:in `from_file'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-1.10.1/lib/cocoapods/config.rb:205:i
n `podfile'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-1.10.1/lib/cocoapods/command.rb:160:
in `verify_podfile_exists!'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-1.10.1/lib/cocoapods/command/install
.rb:46:in `run'
/Library/Ruby/Gems/2.6.0/gems/claide-1.0.3/lib/claide/command.rb:334:in
`run'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-1.10.1/lib/cocoapods/command.rb:52:i
n `run'
/Library/Ruby/Gems/2.6.0/gems/cocoapods-1.10.1/bin/pod:55:in `<top
(required)>'
/usr/local/bin/pod:23:in `load'
/usr/local/bin/pod:23:in `<main>'

Error output from CocoaPods:
↳
/System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/lib/ruby/2.6.0/un
iversal-darwin20/rbconfig.rb:229: warning: Insecure world writable dir
/usr/local/sbin in PATH, mode 040777