patch 9.1.0705: Sorting of fuzzy filename completion is not stable

Problem:  Sorting of fuzzy filename completion is not stable
Solution: Compare indexes when scores are equal.  Fix some typos.
          (zeertzjq)

closes: #15593

Signed-off-by: zeertzjq <zeertzjq@outlook.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/insexpand.c b/src/insexpand.c
index af818d4..d424fff 100644
--- a/src/insexpand.c
+++ b/src/insexpand.c
@@ -3546,7 +3546,8 @@
     int idx_b = *(const int *)b;
     int score_a = compl_fuzzy_scores[idx_a];
     int score_b = compl_fuzzy_scores[idx_b];
-    return (score_a > score_b) ? -1 : (score_a < score_b) ? 1 : 0;
+    return score_a == score_b ? (idx_a == idx_b ? 0 : (idx_a < idx_b ? -1 : 1))
+			: (score_a > score_b ? -1 : 1);
 }
 
 /*