patch 8.1.1438: some commands cause trouble in a popup window

Problem:    Some commands cause trouble in a popup window.
Solution:   Add NOT_IN_POPUP_WINDOW.
diff --git a/src/ex_cmds2.c b/src/ex_cmds2.c
index 5a33bb1..66e5fca 100644
--- a/src/ex_cmds2.c
+++ b/src/ex_cmds2.c
@@ -1864,6 +1864,8 @@
     char_u	*p;
     int		old_arg_idx = curwin->w_arg_idx;
 
+    if (NOT_IN_POPUP_WINDOW)
+	return;
     if (argn < 0 || argn >= ARGCOUNT)
     {
 	if (ARGCOUNT <= 1)