Revert "Update inventory.js (PrismarineJS#3507)"

This reverts commit a0e92ca.

lib/plugins/inventory.js

@@ -263,7 +263,7 @@ function inject (bot, { hideErrors }) {
     const itemType = options.itemType
     const metadata = options.metadata
     const nbt = options.nbt
-    let count = (options.count === undefined || options.count === null) ? 1 : options.count
+    let count = options.count === null ? 1 : options.count
     let firstSourceSlot = null
 
     // ranges