Fix search without querry

App crash when we try to get /search

Add an empty querry '' as default

lib/gollum/app.rb

@@ -438,7 +438,7 @@ module Precious
     end
 
     get '/search' do
-      @query   = params[:q]
+      @query   = params[:q] || ''
       wiki     = wiki_new
       # Sort wiki search results by count (desc) and then by name (asc)
       @results = wiki.search(@query).sort { |a, b| (a[:count] <=> b[:count]).nonzero? || b[:name] <=> a[:name] }.reverse