gnucash maint: [HBCI] Fix crashing aqbanking balance download and import

[Christian Stimming]

Updated	 via  https://github.com/Gnucash/gnucash/commit/64dedccf (commit)
	from  https://github.com/Gnucash/gnucash/commit/3d7e66d9 (commit)



commit 64dedccfe32d8b9620e0df87a992e1fdc74b531b
Author: Christian Stimming <christian at cstimming.de>
Date:   Sun Sep 20 21:04:16 2020 +0200

    [HBCI] Fix crashing aqbanking balance download and import
    
    Also, clarify the preconditions of the import-matcher functions.
    Follow-up to d4fe5841203e6ebdeb1162b76c91026df1d3e034



Summary of changes:
 gnucash/import-export/aqb/gnc-ab-utils.c    | 6 ++++--
 gnucash/import-export/import-main-matcher.c | 5 ++++-
 2 files changed, 8 insertions(+), 3 deletions(-)