gsub fails for where selectors

[jpsimonroy]

Try the below in the specs:
JsonPath.for(@object).gsub!("$..book[?(@['price'] > 20)]") { |p| p + 10 }

It fails with trace:
NoMethodError: undefined method +' for nil:NilClass from (irb):139:inblock in irb_binding'
from /Users/simon/.rvm/gems/ruby-2.1.2@lookist/gems/jsonpath-0.5.6/lib/jsonpath/enumerable.rb:97:in call' from /Users/simon/.rvm/gems/ruby-2.1.2@lookist/gems/jsonpath-0.5.6/lib/jsonpath/enumerable.rb:97:inyield_value'
from /Users/simon/.rvm/gems/ruby-2.1.2@lookist/gems/jsonpath-0.5.6/lib/jsonpath/enumerable.rb:15:in each' from /Users/simon/.rvm/gems/ruby-2.1.2@lookist/gems/jsonpath-0.5.6/lib/jsonpath/enumerable.rb:38:inblock (2 levels) in each'
from /Users/simon/.rvm/gems/ruby-2.1.2@lookist/gems/activesupport-4.1.6/lib/active_support/core_ext/range/each.rb:7:in each' from /Users/simon/.rvm/gems/ruby-2.1.2@lookist/gems/activesupport-4.1.6/lib/active_support/core_ext/range/each.rb:7:ineach_with_time_with_zone'
from /Users/simon/.rvm/gems/ruby-2.1.2@lookist/gems/jsonpath-0.5.6/lib/jsonpath/enumerable.rb:35:in block in each' from /Users/simon/.rvm/gems/ruby-2.1.2@lookist/gems/jsonpath-0.5.6/lib/jsonpath/enumerable.rb:24:ineach'
from /Users/simon/.rvm/gems/ruby-2.1.2@lookist/gems/jsonpath-0.5.6/lib/jsonpath/enumerable.rb:24:in each' from /Users/simon/.rvm/gems/ruby-2.1.2@lookist/gems/jsonpath-0.5.6/lib/jsonpath/enumerable.rb:29:inblock in each'
from /Users/simon/.rvm/gems/ruby-2.1.2@lookist/gems/jsonpath-0.5.6/lib/jsonpath/enumerable.rb:24:in each' from /Users/simon/.rvm/gems/ruby-2.1.2@lookist/gems/jsonpath-0.5.6/lib/jsonpath/enumerable.rb:24:ineach'
from /Users/simon/.rvm/gems/ruby-2.1.2@lookist/gems/jsonpath-0.5.6/lib/jsonpath/enumerable.rb:78:in block in each' from /Users/simon/.rvm/gems/ruby-2.1.2@lookist/gems/jsonpath-0.5.6/lib/jsonpath/enumerable.rb:78:ineach'
from /Users/simon/.rvm/gems/ruby-2.1.2@lookist/gems/jsonpath-0.5.6/lib/jsonpath/enumerable.rb:78:in each' from /Users/simon/.rvm/gems/ruby-2.1.2@lookist/gems/jsonpath-0.5.6/lib/jsonpath/enumerable.rb:18:ineach'
from /Users/simon/.rvm/gems/ruby-2.1.2@lookist/gems/jsonpath-0.5.6/lib/jsonpath/enumerable.rb:20:in each' from /Users/simon/.rvm/gems/ruby-2.1.2@lookist/gems/jsonpath-0.5.6/lib/jsonpath/proxy.rb:40:in_gsub'
from /Users/simon/.rvm/gems/ruby-2.1.2@lookist/gems/jsonpath-0.5.6/lib/jsonpath/proxy.rb:15:in gsub!' from (irb):139 from /Users/simon/.rvm/rubies/ruby-2.1.2/bin/irb:11:in

'

[Skarlso]

Because the correct for the assert is this: JsonPath.for(@object).gsub!('$..book.price[?(@ > 20)]') { |p| p + 10 }