other errors

gistfile1.txt

NoMethodError in ReviewsController#preview
undefined method `to_sym' for nil:NilClass

Extracted source (around line #59):
57
58
59
60
61
62
                
        expanded_attrs = {}
        attrs.each do |attr, value|
          if aggregation = reflect_on_aggregation(attr.to_sym)
            mapping = aggregation.mapping
            mapping.each do |field_attr, aggregate_attr|
              if mapping.size == 1 && !value.respond_to?(aggregate_attr)

Rails.root: /Users/steven/code/testivate

Application Trace | Framework Trace | Full Trace
activerecord (4.2.0) lib/active_record/sanitization.rb:59:in `block in expand_hash_conditions_for_aggregates'
activerecord (4.2.0) lib/active_record/sanitization.rb:58:in `each'
activerecord (4.2.0) lib/active_record/sanitization.rb:58:in `expand_hash_conditions_for_aggregates'
activerecord (4.2.0) lib/active_record/relation/query_methods.rb:955:in `build_where'
activerecord (4.2.0) lib/active_record/relation/query_methods.rb:584:in `where!'
activerecord (4.2.0) lib/active_record/relation/query_methods.rb:574:in `where'
activerecord (4.2.0) lib/active_record/relation.rb:82:in `_update_record'
activerecord (4.2.0) lib/active_record/persistence.rb:512:in `_update_record'
activerecord (4.2.0) lib/active_record/locking/optimistic.rb:70:in `_update_record'
activerecord (4.2.0) lib/active_record/attribute_methods/dirty.rb:123:in `_update_record'
activerecord (4.2.0) lib/active_record/callbacks.rb:310:in `block in _update_record'
activesupport (4.2.0) lib/active_support/callbacks.rb:88:in `call'
activesupport (4.2.0) lib/active_support/callbacks.rb:88:in `_run_callbacks'
activesupport (4.2.0) lib/active_support/callbacks.rb:734:in `_run_update_callbacks'
activerecord (4.2.0) lib/active_record/callbacks.rb:310:in `_update_record'
activerecord (4.2.0) lib/active_record/timestamp.rb:70:in `_update_record'
activerecord (4.2.0) lib/active_record/persistence.rb:501:in `create_or_update'
activerecord (4.2.0) lib/active_record/callbacks.rb:302:in `block in create_or_update'
activesupport (4.2.0) lib/active_support/callbacks.rb:117:in `call'
activesupport (4.2.0) lib/active_support/callbacks.rb:117:in `call'
activesupport (4.2.0) lib/active_support/callbacks.rb:169:in `block in halting'
activesupport (4.2.0) lib/active_support/callbacks.rb:169:in `call'
activesupport (4.2.0) lib/active_support/callbacks.rb:169:in `block in halting'
activesupport (4.2.0) lib/active_support/callbacks.rb:92:in `call'
activesupport (4.2.0) lib/active_support/callbacks.rb:92:in `_run_callbacks'
activesupport (4.2.0) lib/active_support/callbacks.rb:734:in `_run_save_callbacks'
activerecord (4.2.0) lib/active_record/callbacks.rb:302:in `create_or_update'
activerecord (4.2.0) lib/active_record/persistence.rb:120:in `save'
activerecord (4.2.0) lib/active_record/validations.rb:37:in `save'
activerecord (4.2.0) lib/active_record/attribute_methods/dirty.rb:21:in `save'
activerecord (4.2.0) lib/active_record/transactions.rb:286:in `block (2 levels) in save'
activerecord (4.2.0) lib/active_record/transactions.rb:347:in `block in with_transaction_returning_status'
activerecord (4.2.0) lib/active_record/connection_adapters/abstract/database_statements.rb:213:in `block in transaction'
activerecord (4.2.0) lib/active_record/connection_adapters/abstract/transaction.rb:188:in `within_new_transaction'
activerecord (4.2.0) lib/active_record/connection_adapters/abstract/database_statements.rb:213:in `transaction'
activerecord (4.2.0) lib/active_record/transactions.rb:220:in `transaction'
activerecord (4.2.0) lib/active_record/transactions.rb:344:in `with_transaction_returning_status'
activerecord (4.2.0) lib/active_record/transactions.rb:286:in `block in save'
activerecord (4.2.0) lib/active_record/transactions.rb:301:in `rollback_active_record_state!'
activerecord (4.2.0) lib/active_record/transactions.rb:285:in `save'
/Users/steven/.rvm/gems/ruby-2.1.3/bundler/gems/activerecord-session_store-a30ec3117d18/lib/action_dispatch/session/active_record_store.rb:77:in `set_session'
rack (1.6.0) lib/rack/session/abstract/id.rb:342:in `commit_session'
rack (1.6.0) lib/rack/session/abstract/id.rb:226:in `context'
rack (1.6.0) lib/rack/session/abstract/id.rb:220:in `call'
actionpack (4.2.0) lib/action_dispatch/middleware/cookies.rb:560:in `call'
activerecord (4.2.0) lib/active_record/query_cache.rb:36:in `call'
activerecord (4.2.0) lib/active_record/connection_adapters/abstract/connection_pool.rb:647:in `call'
actionpack (4.2.0) lib/action_dispatch/middleware/callbacks.rb:29:in `block in call'
activesupport (4.2.0) lib/active_support/callbacks.rb:88:in `call'
activesupport (4.2.0) lib/active_support/callbacks.rb:88:in `_run_callbacks'
activesupport (4.2.0) lib/active_support/callbacks.rb:734:in `_run_call_callbacks'
activesupport (4.2.0) lib/active_support/callbacks.rb:81:in `run_callbacks'
actionpack (4.2.0) lib/action_dispatch/middleware/callbacks.rb:27:in `call'
actionpack (4.2.0) lib/action_dispatch/middleware/reloader.rb:73:in `call'
actionpack (4.2.0) lib/action_dispatch/middleware/remote_ip.rb:78:in `call'
web-console (2.0.0) lib/action_dispatch/debug_exceptions.rb:18:in `middleware_call'
web-console (2.0.0) lib/action_dispatch/debug_exceptions.rb:13:in `call'
actionpack (4.2.0) lib/action_dispatch/middleware/show_exceptions.rb:30:in `call'
railties (4.2.0) lib/rails/rack/logger.rb:38:in `call_app'
railties (4.2.0) lib/rails/rack/logger.rb:22:in `call'
request_store (1.1.0) lib/request_store/middleware.rb:8:in `call'
actionpack (4.2.0) lib/action_dispatch/middleware/request_id.rb:21:in `call'
rack (1.6.0) lib/rack/methodoverride.rb:22:in `call'
rack (1.6.0) lib/rack/runtime.rb:18:in `call'
activesupport (4.2.0) lib/active_support/cache/strategy/local_cache_middleware.rb:28:in `call'
rack (1.6.0) lib/rack/lock.rb:17:in `call'
actionpack (4.2.0) lib/action_dispatch/middleware/static.rb:113:in `call'
rack (1.6.0) lib/rack/sendfile.rb:113:in `call'
railties (4.2.0) lib/rails/engine.rb:518:in `call'
railties (4.2.0) lib/rails/application.rb:164:in `call'
railties (4.2.0) lib/rails/railtie.rb:194:in `public_send'
railties (4.2.0) lib/rails/railtie.rb:194:in `method_missing'
rack (1.6.0) lib/rack/lint.rb:49:in `_call'
rack (1.6.0) lib/rack/lint.rb:37:in `call'
rack (1.6.0) lib/rack/showexceptions.rb:24:in `call'
rack (1.6.0) lib/rack/commonlogger.rb:33:in `call'
sinatra (1.4.5) lib/sinatra/base.rb:217:in `call'
rack (1.6.0) lib/rack/chunked.rb:54:in `call'
rack (1.6.0) lib/rack/content_length.rb:15:in `call'
unicorn (4.8.3) lib/unicorn/http_server.rb:576:in `process_client'
unicorn (4.8.3) lib/unicorn/http_server.rb:670:in `worker_loop'
unicorn (4.8.3) lib/unicorn/http_server.rb:525:in `spawn_missing_workers'
unicorn (4.8.3) lib/unicorn/http_server.rb:140:in `start'
unicorn (4.8.3) bin/unicorn:126:in `<top (required)>'
/Users/steven/.rvm/gems/ruby-2.1.3/bin/unicorn:23:in `load'
/Users/steven/.rvm/gems/ruby-2.1.3/bin/unicorn:23:in `<main>'
/Users/steven/.rvm/gems/ruby-2.1.3/bin/ruby_executable_hooks:15:in `eval'
/Users/steven/.rvm/gems/ruby-2.1.3/bin/ruby_executable_hooks:15:in `<main>'
Request

Parameters:

{"item"=>"28",
 "page"=>"element",
 "id"=>"60"}
Toggle session dump
Toggle env dump
Response

Headers:

None
>>  

I'm curious. I have this exact same stacktrace and found this gist searching for it. What was it?

I'm having the same issue.
The gist is quite old, but do you remember the solution or have some idea of how to solve it?