Merged revisions 154066 via svnmerge from

https://origsvn.digium.com/svn/asterisk/branches/1.4

........
  r154066 | tilghman | 2008-11-03 16:27:10 -0600 (Mon, 03 Nov 2008) | 5 lines
  
  Attempting to expunge a mailbox when the mailstream is NULL will crash Asterisk.
  (Closes issue #13829)
  Reported by: jaroth
  Patch by: me (modified jaroth's patch)
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git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@154072 65c4cc65-6c06-0410-ace0-fbb531ad65f3

apps/app_voicemail.c

@@ -9296,7 +9296,7 @@ out:
 #ifdef IMAP_STORAGE
 	/* expunge message - use UID Expunge if supported on IMAP server*/
 	ast_debug(3, "*** Checking if we can expunge, deleted set to %d, expungeonhangup set to %d\n",deleted,expungeonhangup);
-	if (vmu && deleted == 1 && expungeonhangup == 1) {
+	if (vmu && deleted == 1 && expungeonhangup == 1 && vms.mailstream != NULL) {
 #ifdef HAVE_IMAP_TK2006
 		if (LEVELUIDPLUS (vms.mailstream)) {
 			mail_expunge_full(vms.mailstream,NIL,EX_UID);