[iagno] Add a fallback for buggy IA.

[Arnaud B. <arnaudb src gnome org>]

commit 03aeaa042030b20166c221338ded98a46333d67b
Author: Arnaud Bonatti <arnaud bonatti gmail com>
Date:   Mon Feb 25 21:57:12 2019 +0100

    Add a fallback for buggy IA.

 src/computer-player.vala | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)
---
diff --git a/src/computer-player.vala b/src/computer-player.vala
index eb99725..96184b9 100644
--- a/src/computer-player.vala
+++ b/src/computer-player.vala
@@ -93,7 +93,16 @@ private class ComputerPlayer : Object
         if (game.place_tile (x, y) == 0)
         {
             critical ("Computer chose an invalid move: %d,%d\n%s", x, y, game.to_string ());
-            assert_not_reached ();
+
+            /* Has been reached, once. So let's have a fallback. */
+            uint8 new_x;
+            uint8 new_y;
+            random_select (game, out new_x, out new_y);
+            if (game.place_tile (new_x, new_y) == 0)
+            {
+                critical ("Computer chose an invalid move for the second time: %d,%d\n%s", new_x, new_y, 
game.to_string ());
+                assert_not_reached ();
+            }
         }
     }