The problem is not actually related to 2byte collation IDs.
The same crash happens if you change the collation ID in
mysql-test/str_data/Index.xml to a value smaller than 256.

Crash happened in SQL parser, because the "ident_map" and "state_map"
arrays were not initialized in loadable utf8 collations.

Fix: adding proper initialization of the "ident_map" and "state_map"
members for loadable utf8 collations.