Fix java.lang.NullPointerException when incorrect schema in database.

[dertalai]

org.hibernate.tool.schema.spi.SchemaManagementException expected instead.

This problem is probably present in newer branches too.

[CLAassistant]

All committers have signed the CLA.

[matrei]

This makes sense as m can be null. However, without a test case, I'm not sure what would cause this to occur or what will happen after this change if it occurs.

[dertalai]

@matrei, not sure how to help. But I can describe how and why I made this change locally.

I'm using this library within a Grails 5 project. Database is MySQL. When database and entities don't match, I get a NullPointerException during application start, no clue what's happening.

Now, when I controlled this null value, I got a meaninful exception instead. For example: org.hibernate.tool.schema.spi.SchemaManagementException: Schema-validation: missing table [table_name].

[matrei]

Thank you @dertalai, that is really good info!

[jdaugherty]

@jamesfredley did you merge this up? the latest version is 9.0.x since we merged the database migration plugin. I didn't think we intended to do older releases in this repo