[PATCH] missing null termination in power supply uevent

Need to null terminate environment. Found by inspection
while looking for similar problems to platform uevent bug
Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org>

drivers/power/power_supply_sysfs.c

@@ -289,6 +289,7 @@ int power_supply_uevent(struct device *dev, char **envp, int num_envp,
 		if (ret)
 			goto out;
 	}
+	envp[i] = NULL;
 
 out:
 	free_page((unsigned long)prop_buf);