patch 8.2.4293: Vim9: when copying a list it gets type list<any>

Problem:    Vim9: when copying a list it gets type list<any> even when the
            original list did not have a type.
Solution:   Only set the type when the original list has a type. (closes #9692)

src/list.c

@@ -1216,7 +1216,11 @@ list_copy(list_T *orig, int deep, int top, int copyID)
     copy = list_alloc();
     if (copy != NULL)
     {
-	copy->lv_type = alloc_type(top || deep ? &t_list_any: orig->lv_type);
+	if (orig->lv_type == NULL)
+	    copy->lv_type = NULL;
+	else
+	    copy->lv_type = alloc_type(top || deep
+						 ? &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

@@ -1495,6 +1495,9 @@ def Test_expr5_list_add()
 
       # result of glob() is "any", runtime type check
       var sl: list<string> = glob('*.txt', false, true) + ['']
+
+      var lln: list<list<number>> = [[1] + [2]]
+      assert_equal([[1, 2]], lln)
   END
   v9.CheckDefAndScriptSuccess(lines)
 enddef

src/version.c

@@ -746,6 +746,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    4293,
 /**/
     4292,
 /**/