missing initialize in J1Spin

[shivupa]

Proposed changes

This was missed in #3257.

What type(s) of changes does this code introduce?

• Bugfix

Does this introduce a breaking change?

• No

What systems has this change been tested on?

AMD workstation

Checklist

Update the following with a yes where the items apply. If you're unsure about any of them, don't hesitate to ask. This is
simply a reminder of what we are going to look for before merging your code.

• Yes. This PR is up to date with current the current state of 'develop'
• Yes. Code added or changed in the PR has been clang-formatted
• No. This PR adds tests to cover any new code, or to catch a bug that is being fixed
• No. Documentation has been added (if appropriate)

[qmc-robot]

Can one of the admins verify this patch?

[prckent]

Test this please

[prckent]

LGTM, subject to CI.

Thanks Shiv! I am resisting commenting on the rest of this older code, which definitely needs some tidying. Clearly this is an improvement though.

[shivupa]

Sure! I am open to cleaning stuff up and would appreciate any specific things that need addressed! Either in this or a separate PR.

[ye-luo]

In the unit test, please add a call to this fixed constructor and call evaluateLog() to validate the results.

[ye-luo]

Test this please