Author: Marina Glancy
MDL-54769 backup: add missing error language string
http://git.moodle.org/gw?p=moodle.git;a=commit;h=88ed1fab627755c8c0b03a53d176aba16b364392
http://github.com/moodle/moodle/commit/88ed1fab627755c8c0b03a53d176aba16b364392
+ 3.1 en [error_question_answers_missing_in_db,core_error]