no date range check for custom date range in New Download

AdMax-Yell-Budgeting-p10-r24318

In New Download (Bidding), select one or more SEs. Change date dropdown to
Custom Date Range...

Set the date start box to a value that is greater than the date end box (ie.
start Jan 10, 2010 and end Jan 9, 2010).

There should be a check to make sure this is not allowed. Instead, the report
processes and uses "All dates up to [today's date]" as the date range.

Should be like Reporting, which gives this error after hitting 'Submit': "The
date range is invalid: The value on the left side must be earlier than the value
on the right side."