[gnome-nibbles] Fix a crash.

[Arnaud B. <arnaudb src gnome org>]

commit 060c03addd0932b0e859db1ec73b9f8776c62182
Author: Arnaud Bonatti <arnaud bonatti gmail com>
Date:   Sun Nov 1 16:23:15 2020 +0100

    Fix a crash.
    
    Fixes #51.

 src/scoreboard.vala | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/src/scoreboard.vala b/src/scoreboard.vala
index d34f042..a41aee1 100644
--- a/src/scoreboard.vala
+++ b/src/scoreboard.vala
@@ -97,8 +97,8 @@ private class PlayerScoreBox : Box
     internal void update_lives (uint8 lives_left)
     {
         /* Remove lost lives - if any */
-        for (uint8 i = (uint8) life_images.size - 1; i >= lives_left; i--)
-            life_images[i].set_opacity (0);
+        for (uint8 i = (uint8) life_images.size; i > lives_left; i--)
+            life_images[i - 1].set_opacity (0);
 
         /* Add new lives - if any */
         for (uint8 i = 0; i < lives_left; i++)