patch 8.0.0253: error when loading session if winminheight is 2

Problem:    When creating a session when winminheight is 2 or larger and
            loading that session gives an error.
Solution:   Also set winminheight before setting winheight to 1. (Rafael
            Bodill, neovim #5717)
diff --git a/src/testdir/test_mksession.vim b/src/testdir/test_mksession.vim
index c19f3c5..77025c8 100644
--- a/src/testdir/test_mksession.vim
+++ b/src/testdir/test_mksession.vim
@@ -101,4 +101,13 @@
   let &wrap = wrap_save
 endfunc
 
+func Test_mksession_winheight()
+  new
+  set winheight=10 winminheight=2
+  mksession! test_mks.out
+  source test_mks.out
+
+  " call delete('test_mks.out')
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab