HID: logitech-dj: fix wrong detection of bad DJ_SHORT output report

HID: logitech-dj: fix wrong detection of bad DJ_SHORT output report

commit b6a57912854e ("HID: logitech-dj: Prevent REPORT_ID_DJ_SHORT
related user initiated OOB write") assumed that all HID devices attached
to the logitech-dj driver was having an output report of DJ_SHORT.

However, on the receiver itself, we have 2 other HID device we attach
here: the mouse emulation and the keyboard emulation. For those devices
the value of rep is NULL and we are triggered a segfault here.

This is doubly required because logitech-dj also handles non DJ devices
that might not have the DJ collection.

Fixes: b6a57912854e ("HID: logitech-dj: Prevent REPORT_ID_DJ_SHORT related user initiated OOB write")
Signed-off-by: Benjamin Tissoires <bentiss@kernel.org>
Signed-off-by: Jiri Kosina <jkosina@suse.com>