insert-ing partial stacks of items duplicates items

[mutability]

Describe the bug

When inserting stackable items into a container, selecting less than the full number of items takes the correct number of items from the source stack, but inserts the full stack into the container, duplicating items.

Steps To Reproduce

1. Create a test character, drop all items/clothes
2. Spawn and wear cargo pants
3. Spawn and drop 20 scrap metal
4. inventory -> cargo pants -> insert -> 10 right-arrow scrap metal.
   Shows ITEMS TO INSERT: 10 of 20 scrap metals (20).
5. Now there is 10 scrap metal left on the ground, and 20 scrap metal in inventory.

Expected behavior

10 scrap metal on the ground, 10 scrap metal in inventory.

Versions and configuration

• OS: Linux
  • OS Version: LSB Version: core-9.20170808ubuntu1-noarch:printing-9.20170808ubuntu1-noarch:security-9.20170808ubuntu1-noarch; Distributor ID: Ubuntu; Description: Ubuntu 18.04.4 LTS; Release: 18.04; Codename: bionic;
• Game Version: 0.E-2607-ga3c5c682ad-dirty [64-bit] (upstream bd62ef6)
• Graphics Version: Tiles
• Game Language: System language []
• Mods loaded: [
  Dark Days Ahead [dda],
  Disable NPC Needs [no_npc_food]
  ]

[stopple]

encountered this issue in Game Version: 0.E-3894-g4929649 [64-bit]