This fixes a bug introduced in backports from kernel 5.1 which makes
ath10k crash on QCA9984 when a station connects. The FW sends a airtime
report, but this station is not yet fully registered and a NULL pointer
is used.
Fixes: 0b2c42ced2 ("mac80211: Update to version 5.2-rc7")
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
