patch 8.2.2176: crash with a sequence of fold commands

Problem:    Crash with a sequence of fold commands.
Solution:   Bail out when there are no folds at all.  Add a test (Dominique
            Pellé) (closes #7515)

src/fold.c

@@ -916,7 +916,7 @@ foldMoveTo(
 	{
 	    if (!foldFind(gap, curwin->w_cursor.lnum - lnum_off, &fp))
 	    {
-		if (!updown)
+		if (!updown || gap->ga_len == 0)
 		    break;
 
 		// When moving up, consider a fold above the cursor; when

src/testdir/test_fold.vim

@@ -852,4 +852,11 @@ func Test_fold_create_delete_create()
   bwipe!
 endfunc
 
+" this was crashing
+func Test_fold_create_delete()
+  new
+  norm zFzFzdzj
+  bwipe!
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab

src/version.c

@@ -750,6 +750,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    2176,
 /**/
     2175,
 /**/