phrase_boundary_step is ignored with morphology

Describe the environment

Manticore Search version: 3.0.0

OS version: 11.2-RELEASE-p4 FreeBSD 11.2-RELEASE-p4 #0: Thu Sep 27 08:16:24 UTC 2018 root@amd64-builder.daemonology.net:/usr/obj/usr/src/sys/GENERIC amd64

Describe the problem

Description of the issue:

phrase_boundary_step is ignored with morphology

Steps to reproduce:

source src_xxx:src_pattern {
        sql_query = SELECT 1, 'hello . world' AS name
}

index xxx {
        type = plain
        source = src_xxx
        path = /db/sphinx/xxx/xxx

        phrase_boundary = .
        phrase_boundary_step = 1000
        index_exact_words = 1
        morphology = lemmatize_ru_all,lemmatize_en_all
}

With this config call select:

mysql> select * from xxx where match('"hello world"');
+------+
| id   |
+------+
|    1 |
+------+

But it should not return result.

Now remove this lines from config:

        index_exact_words = 1
        morphology = lemmatize_ru_all,lemmatize_en_all

Than rebuild index, and then call select:

mysql> select * from xxx where match('"hello world"');
Empty set (0.00 sec)

mysql> select * from xxx where match('"hello world"~2000');
+------+
| id   |
+------+
|    1 |
+------+

That works as expected.

Reproduce the issue with the shown source and index configuration, then query the phrase with morphology enabled and disabled. Trace the phrase_boundary_step handling in the search and morphology code; done means "hello world" returns no result with the boundary step, while "hello world"~2000 still matches as shown.