Fix error for habit deletion

[CasJam]

A return statement was added to the set_habit method in app/controllers/habits_controller.rb.

Previously, when ActiveRecord::RecordNotFound was rescued, head :not_found was called, but the method continued execution. This resulted in @habit being nil, leading to a NoMethodError when subsequent actions attempted to operate on @habit.

The addition of return after head :not_found ensures that the method execution stops immediately when a habit is not found. This prevents the controller action from proceeding with a nil @habit object.

The change resolves the NoMethodError during habit deletion attempts for non-existent habits, ensuring a proper 404 Not Found response instead of a 500 Internal Server Error. Existing habits can now be deleted successfully.