vim-patch:8.2.1554: crash in normal test

Problem:    Crash in normal test.
Solution:   Skip adjusting marks if there are no folds.
07e87e9eb5

src/nvim/fold.c

@@ -1389,6 +1389,10 @@ static void foldMarkAdjustRecurse(
   linenr_T last;
   linenr_T top;
 
+  if (gap->ga_len == 0) {
+    return;
+  }
+
   /* In Insert mode an inserted line at the top of a fold is considered part
    * of the fold, otherwise it isn't. */
   if ((State & INSERT) && amount == (linenr_T)1 && line2 == MAXLNUM)