Minecraft 17w43a, Minecraft 17w43b
This bug was mentioned on the 17w43a changelog. I was requested to report it.
When pressing the hotbar keys (default 1-9) in the search tab of the creative inventory, the item moves to the appropriate slot as expected, but the number/keypress is also sent to the search bar.
1. Search for "ston"
2. Hover over stone
3. Press "1"
4. The stone moves to your inventory. The search bar now says "ston1" (with no results).