Java The Hutt

A short one here. I was working on a new action and view when during my POST I received the following exception:

NoMethodError (You have a nil object when you didn't expect it!
You might have expected an instance of Array.
The error occured while evaluating nil.[]):

The source of this error was this line:

      if params[:commit] == 'Cancel'

Which confused me because params is the hash that's created by default containing all of the form elements I'm posting. A quick look over my code and I saw that I had created a local variable named 'params' in a branch of logic that doesn't even get executed on a POST. So my code looks similar to this:

def my_action

  if request.get?
    params = Hash.new
    # do stuff
  else
    if params[:commit] == 'Cancel' # <-- NoMethodError on a nil object here
      #do stuff
    end
  end
end

Renaming my local variable to something else fixed the problem so this means that despite never being executed the local variable declared 'params' is overriding the default created by rails. I'm still a newbie to ruby and rails but this doesn't seem correct to me as the 'else' clause above never executes the initialization of the new Hash. Perhaps some ruby expert out there can tell me why this is the case, or have I found a bug in rails?