Enforce more than one dot in Galaxies puzzles.

At minimum size (3x3) Galaxies can generate a pre-solved single dot
game.

You have to add and remove a line to get the victory flash which is a
bit weird, so just prevent this.

galaxies.c

@@ -1301,6 +1301,8 @@ generate:
 
     game_update_dots(state);
 
+    if (state->ndots == 1) goto generate;
+
 #ifdef DEBUGGING
     {
         char *tmp = encode_game(state);