remove unused variable
Merge pull request #10486 from vipulnsward/remove_variable

remove unused variable
raise IrreversibleMigration if no column given

fixes #10419

Following code should raise  IrreversibleMigration. But the code was
failing since options is an array and not a hash.

def change
  change_table :users do |t|
    t.remove_index [:name, :email]
  end
end

Fix was to check if the options is a Hash before operating on it.
Merge pull request #10437 from neerajdotname/10419

raise IrreversibleMigration if no column given
let rake tasks be robust to a missing RDoc in Rubinius [Fixes #10462]

See the comment in the rescue clause towards the top of the patch for the rationale.
Fixes #10432 add_column not creating array columns in PostgreSQL

When then PostgreSQL visitor was [added](https://github.com/rails/rails/commit/6b7fdf3bf3675a14eae74acc5241089308153a34)
`add_column` was no longer receiving the column options directly. This
caused the options to be lost along the way.