From: Jia-Ju Bai <redacted>
Date: Tue, 30 Jul 2019 16:08:13 +0800

In phy_led_trigger_change_speed(), there is an if statement on line 48
to check whether phy->last_triggered is NULL: 
    if (!phy->last_triggered)

When phy->last_triggered is NULL, it is used on line 52:
    led_trigger_event(&phy->last_triggered->trigger, LED_OFF);

Thus, a possible null-pointer dereference may occur.

To fix this bug, led_trigger_event(&phy->last_triggered->trigger,
LED_OFF) is called when phy->last_triggered is not NULL.

This bug is found by a static analysis tool STCheck written by
the OSLAB group in Tsinghua University.

Signed-off-by: Jia-Ju Bai <redacted>

Applied, thanks.