Repeatable migrations produce invalid SQL during dry-run

[axelfontaine]

The script generated for a repeatable migration looks like this:

INSERT INTO "MD_CUSTOMER"."flyway_schema_history" ("installed_rank","version","description","type","script","checksum","installed_by","execution_time","success") VALUES (5, 'null', 'create views', 'SQL', 'R__create_views.sql', -467597611, 'SYSTEM', 0, 1);

But the null is in quotes, so it inserts the string 'null' rather than a null value. If I apply the script to the DB then the subsequent migration fails:

 ERROR: Invalid version containing non-numeric characters. Only 0..9 and . are allowed. Invalid version: null

[axelfontaine]

Fixed.