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.

src/eval.c

@@ -395,7 +395,7 @@ skip_expr_concatenate(
     typval_T	rettv;
     int		res;
     int		vim9script = in_vim9script();
-    garray_T    *gap = &evalarg->eval_ga;
+    garray_T    *gap = evalarg == NULL ? NULL : &evalarg->eval_ga;
     int		save_flags = evalarg == NULL ? 0 : evalarg->eval_flags;
     int		evaluate = evalarg == NULL
 			       ? FALSE : (evalarg->eval_flags & EVAL_EVALUATE);

src/fold.c

@@ -1314,7 +1314,7 @@ setManualFoldWin(
 	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;
 	}
@@ -2905,7 +2905,8 @@ foldSplit(
     // any between top and bot, they have been removed by the caller.
     gap1 = &fp->fd_nested;
     gap2 = &fp[1].fd_nested;
-    (void)(foldFind(gap1, bot + 1 - fp->fd_top, &fp2));
+    if (foldFind(gap1, bot + 1 - fp->fd_top, &fp2))
+    {
 	len = (int)((fold_T *)gap1->ga_data + gap1->ga_len - fp2);
 	if (len > 0 && ga_grow(gap2, len) == OK)
 	{
@@ -2918,6 +2919,7 @@ foldSplit(
 	    gap2->ga_len = len;
 	    gap1->ga_len -= len;
 	}
+    }
     fp->fd_len = top - fp->fd_top;
     fold_changed = TRUE;
 }

src/spellfile.c

@@ -816,7 +816,7 @@ read_cnt_string(FILE *fd, int cnt_bytes, int *cntp)
 
     // read the length bytes, MSB first
     for (i = 0; i < cnt_bytes; ++i)
-	cnt = (cnt << 8) + getc(fd);
+	cnt = (cnt << 8) + (unsigned)getc(fd);
     if (cnt < 0)
     {
 	*cntp = SP_TRUNCERROR;

src/spellsuggest.c

@@ -3606,6 +3606,8 @@ check_suggestions(
     int		len;
     hlf_T	attr;
 
+    if (gap->ga_len == 0)
+	return;
     stp = &SUG(*gap, 0);
     for (i = gap->ga_len - 1; i >= 0; --i)
     {

src/version.c

@@ -754,6 +754,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1560,
 /**/
     1559,
 /**/

src/vim9compile.c

@@ -1147,6 +1147,9 @@ generate_NEWLIST(cctx_T *cctx, int count)
     isn->isn_arg.number = count;
 
     // get the member type from all the items on the stack.
+    if (count == 0)
+	member = &t_void;
+    else
 	member = get_member_type_from_stack(
 	    ((type_T **)stack->ga_data) + stack->ga_len, count, 1,
 							  cctx->ctx_type_list);
@@ -1180,6 +1183,9 @@ generate_NEWDICT(cctx_T *cctx, int count)
 	return FAIL;
     isn->isn_arg.number = count;
 
+    if (count == 0)
+	member = &t_void;
+    else
 	member = get_member_type_from_stack(
 	    ((type_T **)stack->ga_data) + stack->ga_len, count, 2,
 							  cctx->ctx_type_list);