[lua] Fixes nil errors in Disaster Idol spell choose

[Frankie-hz]

I affirm:

• I understand that if I do not agree to the following points by completing the checkboxes my PR will be ignored.
• I understand I should leave resolving conversations to the LandSandBoat team so that reviewers won't miss what was said.
• I have read and understood the Contributing Guide and the Code of Conduct.
• I have tested my code and the things my code has changed since the last commit in the PR and will test after any later commits.

What does this pull request do?

Fixes error in spell choose script. The effects were not defined

Steps to test these changes

!spawnmob 17531121
!gotoid 17531121
Fight it on darksday - see no errors