The DB upgrade script version 25 for MS SQL has incorrect syntax. From the forum report;

2019.02.28 13:59:09 org.jivesoftware.database.SchemaManager - SchemaManager: Failed to execute SQL:
{{ DROP INDEX IF EXISTS ofMucConvLog_msg_id;}}
{{ 2019.02.28 13:59:09 org.jivesoftware.database.SchemaManager - Must specify the table name and index name for the DROP INDEX statement.}}

Apparently the correct syntax should be

DROP INDEX IF EXISTS ofMucConvLog_msg_id ON ofMucConversationLog;