Fix for #114

[1sammy]

Describe your changes

Added a check in the GameBorderData constructor that prevents centerLocations from becoming [null] instead of simply null which caused a bug where resetBorder() would not follow the this.centerLocations.isEmpty() path when it should have, causing a NullPointerException and arena-breaking in-game behaviour (broken countdown, no pvp, player immortality).

I'm not sure how this bug came to be as it seems impossible to avoid, possibly a change in truth-value behavior across java versions?

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Target Minecraft Versions: any
Requirements: none
Related Issues: #114

Checklist before requesting a review

• [ Somewhat... I maintained style and there was only one branch available to PR] I have read the contributing guidelines
• Thanks for considering my PR I think it fixes a genuine bug -- I am not a regular open source contributor so sorry if I've done something wrong here plz lmk how I can fix ty
• See attached a plain .patch for this
  0001-null-centerLocations-causing-a-truthy-branch-in-Game.patch