Merged revisions 175590 via svnmerge from

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

........
  r175590 | mmichelson | 2009-02-13 13:47:48 -0600 (Fri, 13 Feb 2009) | 16 lines
  
  Fix a potential crash situation when using IMAP voicemail
  
  If calling into VoiceMailMain when using IMAP storage, it was
  possible to crash Asterisk by hanging up the phone when prompted
  for a voicemail mailbox. This patch fixes the issue.
  
  While it may appear that this patch is superficial, it allows code
  execution to continue to the failure case just below the IMAP_STORAGE
  code block where this patch has been applied
  
  (closes issue #14473)
  Reported by: dwpaul
  Patches:
        voicemail_imap_crash_no_mailbox.patch uploaded by dwpaul (license 689)
........


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@175591 65c4cc65-6c06-0410-ace0-fbb531ad65f3

apps/app_voicemail.c

@@ -8894,7 +8894,8 @@ static int vm_execmain(struct ast_channel *chan, void *data)
 #ifdef IMAP_STORAGE
 	vms.interactive = 1;
 	vms.updated = 1;
-	ast_copy_string(vms.context, vmu->context, sizeof(vms.context));
+	if (vmu)
+		ast_copy_string(vms.context, vmu->context, sizeof(vms.context));
 	vmstate_insert(&vms);
 	init_vm_state(&vms);
 #endif