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.
Example:
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).