patch 8.2.3626: "au! event" cannot be followed by another command

Problem:    "au!" and "au! event" cannot be followed by another command as
            documented.
Solution:   When a bar is found set nextcmd.
diff --git a/src/autocmd.c b/src/autocmd.c
index 14cd4af..ac21196 100644
--- a/src/autocmd.c
+++ b/src/autocmd.c
@@ -845,6 +845,7 @@
 
     if (*arg == '|')
     {
+	eap->nextcmd = arg + 1;
 	arg = (char_u *)"";
 	group = AUGROUP_ALL;	// no argument, use all groups
     }
@@ -869,6 +870,7 @@
     pat = skipwhite(pat);
     if (*pat == '|')
     {
+	eap->nextcmd = pat + 1;
 	pat = (char_u *)"";
 	cmd = (char_u *)"";
     }