Cleanup binstub for rubocop

Author: roberts1000

lib/spring/client/binstub.rb

@@ -34,7 +34,8 @@ class Binstub < Command
   require 'bundler'
 
   lockfile = Bundler::LockfileParser.new(Bundler.default_lockfile.read)
-  if spring = lockfile.specs.detect { |spec| spec.name == "spring" }
+  spring = lockfile.specs.detect { |spec| spec.name == "spring" }
+  if spring
     Gem.use_paths Gem.dir, Bundler.bundle_path.to_s, *Gem.path
     gem 'spring', spring.version
     require 'spring/binstub'