gnucash maint: Bug 798740 - Build fails with gcc 13

[John Ralls]

Updated	 via  https://github.com/Gnucash/gnucash/commit/ce3447e6 (commit)
	from  https://github.com/Gnucash/gnucash/commit/8a167d18 (commit)



commit ce3447e6ea8b2f734b24a2502e865ebbbc21aaaa
Author: John Ralls <jralls at ceridwen.us>
Date:   Mon Jan 30 10:23:05 2023 -0800

    Bug 798740 - Build fails with gcc 13
    
    Protect against passing an lseek failure rv to read().



Summary of changes:
 libgnucash/app-utils/file-utils.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)