How to find nil object error in the rails application?

or you can use it :

Without a backtrace, all I can think of right now is to remove plugins one-by-one until the error goes away. Once you eliminate the error, you’ll know that the last plugin that you removed was causing the problem. Of course, the problem could be caused by the interaction of two or more plugins. Thus, once you’ve identified the offending plugin, you may want to remove all other plugins that you can and try just the offending plugin to see if it still causes problems.

Good luck,