From the image, it shows the pumpkin on the player's head, but it doesn't show up by using /data (Slot 103 is the head slot).

How to reproduce:

• Place a repeating command block that is always active with the following command:
      /item replace entity <player> armor.head with minecraft:air
• Shift-click the wearable headgear into the head slot (it may take a few tries)
• Use /data get entity <player> Inventory