patch 8.2.4295: Vim9: concatenating two lists may result in wrong type

Problem:    Vim9: concatenating two lists may result in wrong type.
Solution:   Remove the type instead of using list<any>. (closes #9692)

src/list.c

@@ -1216,11 +1216,10 @@ list_copy(list_T *orig, int deep, int top, int copyID)
     copy = list_alloc();
     if (copy != NULL)
     {
-	if (orig->lv_type == NULL)
+	if (orig->lv_type == NULL || top || deep)
 	    copy->lv_type = NULL;
 	else
-	    copy->lv_type = alloc_type(top || deep
+	    copy->lv_type = alloc_type(orig->lv_type);
-						 ? &t_list_any: orig->lv_type);
 	if (copyID != 0)
 	{
 	    // Do this before adding the items, because one of the items may

src/testdir/test_vim9_expr.vim

@@ -1500,6 +1500,12 @@ def Test_expr5_list_add()
       assert_equal([[1, 2]], lln)
   END
   v9.CheckDefAndScriptSuccess(lines)
+
+  lines =<< trim END
+      var ln: list<number> = [0]
+      var lln: list<list<number>> = [ln + []]
+  END
+  v9.CheckDefAndScriptSuccess(lines)
 enddef
 
 " test multiply, divide, modulo

src/version.c

@@ -746,6 +746,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    4295,
 /**/
     4294,
 /**/