[GR-57624] Fix Locale NPE in JDK 24+10 and better

[jerboaa]

The JDK's StaticProperty class uses a default of the empty string for the java.locale.useOldISOCodes static property. Ensure to also use the empty string as the default in substratevm avoiding the NullPointerException.

Closes: #9526

Testing:

• Passes the provided reproducer in #9526. Throws NPE before.
• Quarkus tests from https://github.com/graalvm/mandrel/issues/778 which triggered this investigation.

[jerboaa]

@fniephaus Is this something the Oracle GraalVM team is aware of? Thanks!

[fniephaus]

Hi @jerboaa, I don't think we are aware of this, but let me change that ;) Thanks for the PR and the ping!

[jerboaa]

@fniephaus Hi! Any update on this?

[fniephaus]

Thanks for the reminder, @jerboaa. I'm working on integrating this.

[jerboaa]

Thank you!