Improved getItem inventory matching and fix inventory being stuck

[swkeep]

Description

Just two small fixes:

1. Fixed inventoryId matching in getItem. Without using the character starting index in find, names ending with "drop-" couldn't be used (ammoDrop, cargoDrop, etc) and we can't use underscores in names because of how find works:

   -- both of these return the same result
   print(('drop-'):find('drop-'))
   print(('drop_'):find('drop-'))

2. Fixed an issue where players could get stuck in inv_busy = true state, if they had their inventory open before we restarted the inventory. This one typically is not an issue for most servers, but developers may notice it.

   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.