Make it rain in SDL tiles again

Now that `map::draw` is not called when tiles are enabled (perhaps #7116), `g->mapRain` is not filled with any values.
Therefor the rain animation code (see `game::get_player_input`) can not place any raindrops on the screen and `g->wPrint.vdrops` stays empty.
And so cata_tiles tries to show raindrops, but as the list of raindrop locations is empty it will not draw any.

Added filling the values to `mapRain` from `cata_tiles`.