vim-patch:8.2.1560: using NULL pointers in some code

Problem:    Using NULL pointers in some code. (James McCoy)
Solution:   Avoid adding to a NULL pointer.  Use byte as unsigned.
https://github.com/vim/vim/commit/9c2b06637b32742cac11bfd66b1a4e84583c6c2e

The changes to eval.c (skip_expr_concatenate) and vim9compile.c aren't
included since they're specific to vim9script support.

2 files changed, 16 insertions, 12 deletions

diff --git a/src/nvim/fold.c b/src/nvim/fold.c
index 3d631a158e..a197be28d7 100644
--- a/src/nvim/fold.c
+++ b/src/nvim/fold.c
@@ -1232,7 +1232,7 @@ setManualFoldWin(
   for (;; ) {
     if (!foldFind(gap, lnum, &fp)) {
       /* If there is a following fold, continue there next time. */
-      if (fp < (fold_T *)gap->ga_data + gap->ga_len)
+      if (fp != NULL && fp < (fold_T *)gap->ga_data + gap->ga_len)
         next = fp->fd_top + off;
       break;
     }
@@ -2615,17 +2615,18 @@ static void foldSplit(buf_T *buf, garray_T *const gap,
    * any between top and bot, they have been removed by the caller. */
   garray_T *const gap1 = &fp->fd_nested;
   garray_T *const gap2 = &fp[1].fd_nested;
-  (void)(foldFind(gap1, bot + 1 - fp->fd_top, &fp2));
-  const int len = (int)((fold_T *)gap1->ga_data + gap1->ga_len - fp2);
-  if (len > 0) {
-    ga_grow(gap2, len);
-    for (int idx = 0; idx < len; idx++) {
-      ((fold_T *)gap2->ga_data)[idx] = fp2[idx];
-      ((fold_T *)gap2->ga_data)[idx].fd_top
-        -= fp[1].fd_top - fp->fd_top;
-    }
-    gap2->ga_len = len;
-    gap1->ga_len -= len;
+  if (foldFind(gap1, bot + 1 - fp->fd_top, &fp2)) {
+    const int len = (int)((fold_T *)gap1->ga_data + gap1->ga_len - fp2);
+    if (len > 0) {
+      ga_grow(gap2, len);
+      for (int idx = 0; idx < len; idx++) {
+        ((fold_T *)gap2->ga_data)[idx] = fp2[idx];
+        ((fold_T *)gap2->ga_data)[idx].fd_top
+          -= fp[1].fd_top - fp->fd_top;
+      }
+      gap2->ga_len = len;
+      gap1->ga_len -= len;
+    }
   }
   fp->fd_len = top - fp->fd_top;
   fold_changed = true;
diff --git a/src/nvim/spell.c b/src/nvim/spell.c
index ad235f1f14..05bb501fa2 100644
--- a/src/nvim/spell.c
+++ b/src/nvim/spell.c
@@ -5663,6 +5663,9 @@ check_suggestions (
   int len;
   hlf_T attr;
 
+  if (gap->ga_len == 0) {
+    return;
+  }
   stp = &SUG(*gap, 0);
   for (int i = gap->ga_len - 1; i >= 0; --i) {
     // Need to append what follows to check for "the the".