gnucash maint: Ensure all uses of g_table_index are protected from NULL return values.

[John Ralls]

Updated	 via  https://github.com/Gnucash/gnucash/commit/a4773d2b (commit)
	from  https://github.com/Gnucash/gnucash/commit/2bc7d314 (commit)



commit a4773d2ba7d05f973f44eb9be1af866576131150
Author: John Ralls <jralls at ceridwen.us>
Date:   Fri Nov 8 13:12:05 2019 -0800

    Ensure all uses of g_table_index are protected from NULL return values.
    
    Including all of the convenience wrappers.
    
    Also remove a few calls where the result is discarded, as it has no
    side effects.



Summary of changes:
 .../register/ledger-core/gncEntryLedgerControl.c   |  1 -
 .../register/ledger-core/split-register-control.c  |  1 -
 gnucash/register/register-gnome/gnucash-header.c   |  4 +--
 gnucash/register/register-gnome/gnucash-sheet.c    | 13 ++++++--
 gnucash/register/register-gnome/gnucash-style.c    | 38 ++++++++++++++++++++--
 5 files changed, 48 insertions(+), 9 deletions(-)