patch 8.2.1472: ":argdel" does not work like ":.argdel" as documented

Problem:    ":argdel" does not work like ":.argdel" as documented. (Alexey
            Demin)
Solution:   Make ":argdel" work like ":.argdel". (closes #6727)
            Also fix giving the error "0 more files to edit".
diff --git a/src/ex_docmd.c b/src/ex_docmd.c
index c08524f..612d478 100644
--- a/src/ex_docmd.c
+++ b/src/ex_docmd.c
@@ -5022,7 +5022,7 @@
     int	    n = ARGCOUNT - curwin->w_arg_idx - 1;
 
     if (!forceit && only_one_window()
-	    && ARGCOUNT > 1 && !arg_had_last && n >= 0 && quitmore == 0)
+	    && ARGCOUNT > 1 && !arg_had_last && n > 0 && quitmore == 0)
     {
 	if (message)
 	{