qemu-char: don't leak opts on error

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>

qemu-char.c

@@ -3178,7 +3178,7 @@ CharDriverState *qemu_chr_new_from_opts(QemuOpts *opts,
     if (i == NULL) {
         error_setg(errp, "chardev: backend \"%s\" not found",
                    qemu_opt_get(opts, "backend"));
-        return NULL;
+        goto err;
     }
 
     if (!cd->open) {