i2c: slave: add sanity check when unregistering

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Alain Volmat <alain.volmat@st.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>

drivers/i2c/i2c-core-slave.c

@@ -58,6 +58,9 @@ int i2c_slave_unregister(struct i2c_client *client)
 {
 	int ret;
 
+	if (IS_ERR_OR_NULL(client))
+		return -EINVAL;
+
 	if (!client->adapter->algo->unreg_slave) {
 		dev_err(&client->dev, "%s: not supported by adapter\n", __func__);
 		return -EOPNOTSUPP;