Fix forgotten NULL check.

[Christian Stimming]

Log Message:
-----------
Fix forgotten NULL check.

2005-04-21  Christian Stimming  <stimming at tuhh.de>

	* src/import-export/hbci/gnc-hbci-getbalance.c: Fix forgotten NULL
	check as reported by Martin Preuss <aquamaniac at gmx.de>.

Modified Files:
--------------
    gnucash:
        ChangeLog
    gnucash/src/import-export/hbci:
        gnc-hbci-getbalance.c