I fixed this, and it is submitted as: https://github.com/MariaDB/server/pull/1162
I also fixed 20 other occurrences of "refering" (changed to "referring") from latest 10.3 code base (included in the same commit):
c:\wpafb\hangar18\10.3\server>grep -r "refering" .
./mysql-test/include/mix2.inc:# Test problem with refering to different fields in same table in UNION
./mysql-test/main/default.result:ERROR 01000: Expression for field `a` is refering to uninitialized field `b`
./mysql-test/main/default.result:ERROR 01000: Expression for field `a` is refering to uninitialized field `a`
./mysql-test/main/default.result:ERROR 01000: Expression for field `b` is refering to uninitialized field `c`
./mysql-test/main/default.result:ERROR 01000: Expression for field `a` is refering to uninitialized field `a`
./mysql-test/main/default.result:ERROR 01000: Expression for field `a` is refering to uninitialized field `b`
./mysql-test/main/default.result:ERROR 01000: Expression for field `a` is refering to uninitialized field `b`
./mysql-test/main/default.result:ERROR 01000: Expression for field `a` is refering to uninitialized field `b`
./mysql-test/main/default.result:ERROR 01000: Expression for field `col1` is refering to uninitialized field `col1`
./mysql-test/main/insert.test:# Test of refering to old values
./mysql-test/suite/gcol/r/gcol_column_def_options_innodb.result:ERROR 01000: Expression for field `b` is refering to uninitialized field `b`
./mysql-test/suite/gcol/r/gcol_column_def_options_innodb.result:ERROR 01000: Expression for field `b` is refering to uninitialized field `c`
./mysql-test/suite/gcol/r/gcol_column_def_options_innodb.result:ERROR 01000: Expression for field `a` is refering to uninitialized field `a`
./mysql-test/suite/gcol/r/gcol_column_def_options_myisam.result:ERROR 01000: Expression for field `b` is refering to uninitialized field `b`
./mysql-test/suite/gcol/r/gcol_column_def_options_myisam.result:ERROR 01000: Expression for field `b` is refering to uninitialized field `c`
./mysql-test/suite/gcol/r/gcol_column_def_options_myisam.result:ERROR 01000: Expression for field `a` is refering to uninitialized field `a`
./mysql-test/suite/innodb/t/innodb.test:# Test problem with refering to different fields in same table in UNION
./mysql-test/suite/vcol/r/vcol_misc.result:ERROR 01000: Expression for field `b` is refering to uninitialized field `b`
./sql/item.cc: Check that we are not refering to any not yet initialized fields
./sql/share/errmsg-utf8.txt: eng "Expression for field %`-.64s is refering to uninitialized field %`s"
./sql/table.cc: /* Check that expressions aren't refering to not yet initialized fields */
I fixed this, and it is submitted as: https://github.com/MariaDB/server/pull/1162
I also fixed 20 other occurrences of "refering" (changed to "referring") from latest 10.3 code base (included in the same commit):
c:\wpafb\hangar18\10.3\server>grep -r "refering" .
./mysql-test/include/mix2.inc:# Test problem with refering to different fields in same table in UNION
./mysql-test/main/default.result:ERROR 01000: Expression for field `a` is refering to uninitialized field `b`
./mysql-test/main/default.result:ERROR 01000: Expression for field `a` is refering to uninitialized field `a`
./mysql-test/main/default.result:ERROR 01000: Expression for field `b` is refering to uninitialized field `c`
./mysql-test/main/default.result:ERROR 01000: Expression for field `a` is refering to uninitialized field `a`
./mysql-test/main/default.result:ERROR 01000: Expression for field `a` is refering to uninitialized field `b`
./mysql-test/main/default.result:ERROR 01000: Expression for field `a` is refering to uninitialized field `b`
./mysql-test/main/default.result:ERROR 01000: Expression for field `a` is refering to uninitialized field `b`
./mysql-test/main/default.result:ERROR 01000: Expression for field `col1` is refering to uninitialized field `col1`
./mysql-test/main/insert.test:# Test of refering to old values
./mysql-test/suite/gcol/r/gcol_column_def_options_innodb.result:ERROR 01000: Expression for field `b` is refering to uninitialized field `b`
./mysql-test/suite/gcol/r/gcol_column_def_options_innodb.result:ERROR 01000: Expression for field `b` is refering to uninitialized field `c`
./mysql-test/suite/gcol/r/gcol_column_def_options_innodb.result:ERROR 01000: Expression for field `a` is refering to uninitialized field `a`
./mysql-test/suite/gcol/r/gcol_column_def_options_myisam.result:ERROR 01000: Expression for field `b` is refering to uninitialized field `b`
./mysql-test/suite/gcol/r/gcol_column_def_options_myisam.result:ERROR 01000: Expression for field `b` is refering to uninitialized field `c`
./mysql-test/suite/gcol/r/gcol_column_def_options_myisam.result:ERROR 01000: Expression for field `a` is refering to uninitialized field `a`
./mysql-test/suite/innodb/t/innodb.test:# Test problem with refering to different fields in same table in UNION
./mysql-test/suite/vcol/r/vcol_misc.result:ERROR 01000: Expression for field `b` is refering to uninitialized field `b`
./sql/item.cc: Check that we are not refering to any not yet initialized fields
./sql/share/errmsg-utf8.txt: eng "Expression for field %`-.64s is refering to uninitialized field %`s"
./sql/table.cc: /* Check that expressions aren't refering to not yet initialized fields */