Fix off-by-one error in TArray::prepare_to_handle

[dnchattan]

Description
Fixes #435 (forked from it's original issue). The new array size is incorrectly computed in TArray::prepare_to_handle and targets a size that is 1 less than the intended array size. This causes it to not zero out and resize except for when you add additional elements after it- this leaves a trail of zeroed out entries, with one "missing" because the size was off for each call.

Fixes # (issue) (if applicable)

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)

How Has This Been Tested?

Verified the following script reproduces the issue and outputs garbage for [4] and [5] the first time, and 0x0000 for [4] the second time ([5] still garbage). Updated code and tested script to confirm both iterations output 0x0000 for [4] and [5]. Additionally stepped through each iteration in the debugger to confirm the correct calls and values were being made.

print("TEST SCRIPT LOADED")

function printBaseId(ar, idx)
    local campId = ar[idx]
    print(string.format("BaseCampIds[%d] 0x%X%X%X%X", idx, campId.A, campId.B, campId.C, campId.D))
end

function printBases()
    PalGroupGuildBase = FindFirstOf("PalGroupGuildBase")
    if PalGroupGuildBase == nil then
        print("PalGroupGuildBase not found")
        return
    end
    print("-- dump BaseCampIds[1-5] --")
    for idx = 1, 5 do
        printBaseId(PalGroupGuildBase.BaseCampIds, idx)
    end
    print("-- repeat --")
    print("-- dump BaseCampIds[1-5] --")
    for idx = 1, 5 do
        printBaseId(PalGroupGuildBase.BaseCampIds, idx)
    end
    
end

RegisterKeyBind(Key.Z, printBases)

Checklist

• I have performed a self-review of my own code.
• I have commented my code, particularly in hard-to-understand areas.
• I have made corresponding changes to the documentation.
• I have added the necessary description of this PR to the changelog, and I have followed the same format as other entries.
• Any dependent changes have been merged and published in downstream modules.

Screenshots (if appropriate)

Additional context

Add any other context about the pull request here.