patch 8.2.2594: alternate buffer added to session file even when it's hidden

Problem:    Alternate buffer added to session file even when it's hidden.
Solution:   Check the 'buflisted' option. (closes #7951)
diff --git a/src/testdir/test_mksession.vim b/src/testdir/test_mksession.vim
index eb8c6a5..6e36553 100644
--- a/src/testdir/test_mksession.vim
+++ b/src/testdir/test_mksession.vim
@@ -544,6 +544,20 @@
   %bwipe
 endfunc
 
+func Test_mksession_no_balt()
+  edit Xtestfile1
+  edit Xtestfile2
+
+  bdelete Xtestfile1
+  mksession! Xtestview
+
+  source Xtestview
+  call assert_equal(0, buflisted('Xtestfile1'))
+
+  call delete('Xtestview')
+  %bwipe
+endfunc
+
 " Test :mkview with a file argument.
 func Test_mkview_file()
   " Create a view with line number and a fold.