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/testdir/dumps/Test_pum_highlights_15.dump b/src/testdir/dumps/Test_pum_highlights_15.dump
index e923b43..199f753 100644
--- a/src/testdir/dumps/Test_pum_highlights_15.dump
+++ b/src/testdir/dumps/Test_pum_highlights_15.dump
@@ -1,4 +1,4 @@
-|/+0&#ffffff0|n|o|n|_|e|x|i|t|_|f|o|l|d|e|r> @58
+|/+0&#ffffff0|n|o|n|_|e|x|i|s|t|i|n|g|_|f|o|l|d|e|r> @54
 |~+0#4040ff13&| @73
 |~| @73
 |~| @73
diff --git a/src/testdir/test_popup.vim b/src/testdir/test_popup.vim
index fe958da..caec8ff 100644
--- a/src/testdir/test_popup.vim
+++ b/src/testdir/test_popup.vim
@@ -1494,7 +1494,7 @@
   call VerifyScreenDump(buf, 'Test_pum_highlights_11', {})
 
   " issue #15357
-  call term_sendkeys(buf, "\<ESC>S/non_exit_folder\<C-X>\<C-F>")
+  call term_sendkeys(buf, "\<ESC>S/non_existing_folder\<C-X>\<C-F>")
   call TermWait(buf, 50)
   call VerifyScreenDump(buf, 'Test_pum_highlights_15', {})