When in creative mode with the Survival Inventory tab selected, resizing the minecraft window will make a stone item appear over the Destroy Item slot. It's not just a texture; hovering over it does show the item text, but clicking it doesn't do anything, and Destroy Item works just fine. Reopening the inventory or changing tabs makes it disappear.
To replicate, open the creative menu to the Survival Inventory tab, then resize the minecraft window. You may need to do it again if the window changes (different bug - MC-132061).
*Note: In the screenshot, I was using custom resource and data packs, but I checked and they aren't the issue - the bug persists without them.
Linked issues
is duplicated by 3
MC-132271
Stone item in clear item box
Resolved
MC-133594
Opening or closing full screen mode or adjusting the size of the window will result in an item (generally stone) on the lower right of the "survival mode bar" in the creation mode item bar display
Resolved
MC-135251
Item in "Destroy Item" slot after resizing window
Resolved
Can confirm for 1.13-pre4