maria_open() fails with error 126 on a freshly created internal temporary table with keys=0, uniques=1

Observed once. create_internal_tmp_table created an Aria internal temporary table successfully, and the immediately following maria_open() in open_tmp_table failed:

[Warning] mariadbd: Got error '126 "Index is corrupted"' for '(null)'
[ERROR] mariadbd: Can't find record in '(temporary)'

The (null) table name is consistent with failure inside maria_open before the share is named. The resulting ER_KEY_NOT_FOUND (1032) then drove cleanup, which crashed separately — see MDEV-41294. Table characteristics from the core: keys=0, uniques=1 (hash unique from the converted distinct index), 5 fields, reclength=198, one Field_blob of length 16777215 from GROUP_CONCAT(DISTINCT ...), tmpdir on a dedicated filesystem.

The offending code seems to be in ha_maria.cc, line 2858 (in 10.11.19):

void ha_maria::drop_table(const char *name)

{ DBUG_ASSERT(!file || file->s->temporary); file->s->deleting= 1; // Do not flush data (void) ha_close(); (void) maria_delete_table_files(name, 1, MY_WME); }

The DBUG_ASSERT call is okay with file being NULL, but then it is immediately dereferenced.