mod_chanserv: Add missing check for NULL mysql.

Add check in channel_get_entrymsg to abort if mysql is NULL,
due to failing to connect to the database. Every other call
to mysql_stmt_init was preceded by such a check except this one,
which naturally was observed triggering some crashes.

LBBS-50 #close

modules/mod_chanserv.c

@@ -323,6 +323,7 @@ static int channel_get_entrymsg(MYSQL_STMT *stmt, const char *channel, char *buf
 	if (!stmt) {
 		connlocal = 1;
 		mysql = sql_connect_db(buf_dbhostname, buf_dbusername, buf_dbpassword, buf_dbname);
+		NULL_RETURN(mysql);
 		stmt = mysql_stmt_init(mysql);
 		if (!stmt) {
 			goto cleanup;