ydb_node_previous_s() returns *ret_subs_used=0 when returning unsubscripted variable

Final Release Note

ydb_node_previous_s() returns with *ret_subs_used set to 0 in case the returned node is the unsubscripted variable. Previously, it would incorrectly return with *ret_subs_used set to YDB_NODE_END when the base variable was a global variable and terminate with a segmentation violation (SIG-11) when the base variable was a local variable. [#398 (closed)]

Description

This issue was observed as part of coming up with a new simpleapi/gvnlvnnodeprev subtest to test ydb_node_previous_s() functionality.

Draft Release Note

ydb_node_previous_s() returns with *ret_subs_used set to 0 in case the returned node is the unsubscripted base variable. Previously, it used to incorrectly return with *ret_subs_used set to YDB_NODE_END in this case when the base variable is a global variable and used to terminate abnormally (SIG-11) when the base variable is a local variable.