letterrip: Don't bring up modal for selecting blank tile when first clicking it

letterrip: Don't bring up modal for selecting blank tile when first clicking it

Instead, just select the tile on first click, and then bring up the
selection modoal on the second click, (either when selecting the
destination cell for movement or deselecting it).

This is consistent behavior with what the user will have first seen
when moving the blank from the rack to the board, and now means that
the user can use click-to-select/click-to-move to move a blank tile
from one board square to another, (which was impossible prior to this
commit).