Budget period entry without interval gives error (BZ#553)

[tbm]

Note: the issue was created automatically with bugzilla2github

Bugzilla bug ID: BZ#553
From: seanh

[tbm]

Comment author: seanh

Budget entries without intervals such as this one:

~ from 1 Sep 2011 to 30 May 2012
  Expenses:Misc  $400
  Assets

cause an error like "Error: Cannot increment a date interval without a duration" when ledger is run with the --budget option (e.g. --budget balance or --budget register). The error occurs when ledger hits a transaction that hits the budget entry. The docs say that period entries don't require an interval.

Adding an interval to the budget period gets rid of the error, e.g.

~ Every 100 years from 1 Sep 2011 to 30 May 2012