Fixed a bug where a card you dragged onto the board could stay frozen in the middle of the screen.
Other changes
Fixed: if the game missed the moment you let go of a dragged card (a short lag, letting go outside the window, a second finger on the screen), the next tap played the card but left a copy of it frozen on the board until the next drag. Now the drag ends cleanly and the card goes back to your hand.
A drag also ends when you switch to another window or app, and a second finger no longer moves the card you are dragging.
