res_pjsip_outbound_registration: Fix race condition when reloading and listing registrations.

Due to the split of outbound registration state from configuration it is possible during
a reload for a "pjsip show registrations" CLI command to be executed which gets an older
snapshot of the configuration. This configuration may include outbound registrations which
have been removed due to a reload operation occurring at the same time. The code for
printing the outbound registration did not take this into account but now it does.

AST-1506 #close

Review: https://reviewboard.asterisk.org/r/4338/
........

Merged revisions 430664 from http://svn.asterisk.org/svn/asterisk/branches/13


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@430665 65c4cc65-6c06-0410-ace0-fbb531ad65f3

res/res_pjsip_outbound_registration.c

@@ -1503,6 +1503,10 @@ static int cli_print_body(void *obj, void *arg, int flags)
 
 	ast_assert(context->output_buffer != NULL);
 
+	if (!state) {
+		return 0;
+	}
+
 	ast_str_append(&context->output_buffer, 0, " %-s/%-*.*s  %-16s  %-16s\n",
 		id,
 		(int) (REGISTRATION_URI_FIELD_LEN - strlen(id)),