Why am I getting a NoMethodError in Users#index error (Ruby on Rails)

Why am I getting a NoMethodError in Users#index error (Ruby on Rails)

References

Reference NO 1

http://stackoverflow.com/questions/15196960/why-am-i-getting-a-nomethoderror-in-usersindex-error-ruby-on-rails

Reference NO 2

http://stackoverflow.com/questions/7167560/why-am-i-getting-a-no-method-and-nil-object-error-in-the-following-line-of-codes

Reference NO 3

http://stackoverflow.com/questions/8844876/nomethoderror-in-usersshow

Reference NO 4

http://stackoverflow.com/questions/5919110/rails-3-tutorial-10-4-2-nomethoderror-undefined-method-admin-for-nilnilcla

Reference NO 5

http://stackoverflow.com/questions/8022587/nomethoderror-in-controlleraction-undefined-method-keynote-for-user0x007

Reference NO 6

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Reference NO 7

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Reference NO 8

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