Raise when formula name is empty

P.S. That still doesn't check if the name is invalid, like "34"

Library/Homebrew/formula_creator.rb

@@ -50,6 +50,7 @@ module Homebrew
     end
 
     def write_formula!
+      raise "name should not be empty" if @name.to_s == ''
       path = @tap.new_formula_path(@name)
       raise "#{path} already exists" if path.exist?