Don't attempt to require nil

Fixes Homebrew/homebrew#28942.

1 files changed, 1 insertions, 1 deletions

diff --git a/Library/brew.rb b/Library/brew.rb
index 280333943..6d7eb3d6f 100755
--- a/Library/brew.rb
+++ b/Library/brew.rb
@@ -108,7 +108,7 @@ begin
       ENV["HOMEBREW_#{e}"] = Object.const_get("HOMEBREW_#{e}").to_s
     end
     exec "brew-#{cmd}", *ARGV
-  elsif require? which("brew-#{cmd}.rb")
+  elsif (path = which("brew-#{cmd}.rb")) && require?(path)
     exit Homebrew.failed? ? 1 : 0
   else
     onoe "Unknown command: #{cmd}"