fix(drops): prevent drop deletion if first slot is nil due to empty indexes

[Qwerty1Verified]

Description

This PR changes the items table for drops to overwrite the length operator meaning the table length will be checked appropriately if the index is unordered. This fixes drops being deleted if an item space isn't filled in order.

Checklist

• [x] I have personally loaded this code into an updated qbcore project and checked all of its functionality.
• [x] My code fits the style guidelines.
• [x] My PR fits the contribution guidelines.