When a sign is placed on any block. My hotbar slot is switched to the before one.( If you can't understand pls watch video or read discription)

When i place a sign , on or in the side of any block,My hotbar slot switches to the before one.

Explanation:- If i have a sign on my 9th hotbar slot, When i place it, The game switches my selected hotbar slot to the 8th hotbar slot. 

 

How to reproduce:- Place any block, then place a sign either on top of it or in the side of the block. The game then changes you selected hotbar slot to the before one.

 

Expected result:- Placing a sign on the block does not have any effect on selected hotbar slot.

 

Actual result:- Placing a sign on a block changes your hotbar slot to the before one.