Use ternary instead of inline rescue

Library/Homebrew/tab.rb

@@ -92,7 +92,7 @@ class Tab < OpenStruct
   def self.dummy_tab f=nil
     attributes = {
       :used_options => [],
-      :unused_options => (f.options.as_flags rescue []),
+      :unused_options => f ? f.options.as_flags : [],
       :built_as_bottle => false,
       :poured_from_bottle => false,
       :tapped_from => "",