Dark Prince:
If the player to make move #50 wants to call it a draw and 50 moves by the opponent were already made without a capture, that player may invoke the draw rule before moving by stating the intention of not making a capture on that move. It must be clear, however, that the move choices available do not require any piece to move onto a square occupied by an enemy piece.

Offering a draw to the opponent under those conditions is considered invoking the draw rule even if the opponent refuses the offer. I would hope that support would be able to verify that the offer had been made. If that's not the case, and the opponent declines or doesn't respond to the offer quickly, the player wanting to invoke the rule should inform support before moving, and then move to avoid timing out.