Update rails_best_practices.rb

This is a fix for following error - 

/home/xpanxion/.rvm/gems/ruby-1.9.2-p320/gems/metric_fu-4.3.1/lib/metric_fu/metrics/rails_best_practices/rails_best_practices.rb:48:in `block in per_file_info': undefined method `split' for nil:NilClass (NoMethodError)
	from /home/xpanxion/.rvm/gems/ruby-1.9.2-p320/gems/metric_fu-4.3.1/lib/metric_fu/metrics/rails_best_practices/rails_best_practices.rb:41:in `each'
	from /home/xpanxion/.rvm/gems/ruby-1.9.2-p320/gems/metric_fu-4.3.1/lib/metric_fu/metrics/rails_best_practices/rails_best_practices.rb:41:in `per_file_info'
	from /home/xpanxion/.rvm/gems/ruby-1.9.2-p320/gems/metric_fu-4.3.1/lib/metric_fu/reporting/result.rb:48:in `add'
	from /home/xpanxion/.rvm/gems/ruby-1.9.2-p320/gems/metric_fu-4.3.1/lib/metric_fu/run.rb:23:in `block in measure'
	from /home/xpanxion/.rvm/gems/ruby-1.9.2-p320/gems/metric_fu-4.3.1/lib/metric_fu/run.rb:21:in `each'
	from /home/xpanxion/.rvm/gems/ruby-1.9.2-p320/gems/metric_fu-4.3.1/lib/metric_fu/run.rb:21:in `measure'
	from /home/xpanxion/.rvm/gems/ruby-1.9.2-p320/gems/metric_fu-4.3.1/lib/metric_fu/run.rb:10:in `run'
	from /home/xpanxion/.rvm/gems/ruby-1.9.2-p320/gems/metric_fu-4.3.1/lib/metric_fu/cli/helper.rb:11:in `run'
	from /home/xpanxion/.rvm/gems/ruby-1.9.2-p320/gems/metric_fu-4.3.1/lib/metric_fu/cli/client.rb:18:in `run'
	from /home/xpanxion/.rvm/gems/ruby-1.9.2-p320/gems/metric_fu-4.3.1/bin/metric_fu:9:in `<top (required)>'
	from /home/xpanxion/.rvm/gems/ruby-1.9.2-p320/bin/metric_fu:19:in `load'
	from /home/xpanxion/.rvm/gems/ruby-1.9.2-p320/bin/metric_fu:19:in `<main>'
	from /home/xpanxion/.rvm/gems/ruby-1.9.2-p320/bin/ruby_noexec_wrapper:14:in `eval'
	from /home/xpanxion/.rvm/gems/ruby-1.9.2-p320/bin/ruby_noexec_wrapper:14:in `<main>'


Error generated for following line --

"------------------"
{:file=>"app/models/building/processing_request.rb", :line=>nil, :problem=>"check 'save' return value or use 'save!'"}
"------------------"