NoMethodError in PublicController#search

undefined method `split' for nil:NilClass

Extracted source (around line #218):
216
217
218
219
220
221
          
@pageid = Page.all
@strisrt = Sanitize.clean(params[:search_string])
@seperateword = @strisrt.split(' ')
@videosearch = VideoTag.search @strisrt,@strisrt.capitalize,@strisrt.upcase,@strisrt.downcase,@strisrt.split(' ').map {|w| w.capitalize }.join(' ')
@subjectsearchrsult = Subject.search @strisrt,@strisrt.capitalize,@strisrt.upcase,@strisrt.downcase,@strisrt.split(' ').map {|w| w.capitalize }.join(' ')

Rails.root: /home/rails

Application Trace | Framework Trace | Full Trace
app/controllers/public_controller.rb:218:in `search'

Request

Parameters:

{"id"=>"Tumour,
"}

Response

Headers:

None