net: dhcpv4: Do not debug print IP address using NULL pointer
net: dhcpv4: Do not debug print IP address using NULL pointer

The ciaddr can be null in requesting state so do not try to print
it in that case.

Fixes #9575

Signed-off-by: Jukka Rissanen <f9f077d1da4c7aa947f9864fa5a28c3588f6a45d@linux.intel.com>

ldts/zephyr,finikorg/zephyr,kraj/zephyr,GiulianoFranchetto/zephyr,Vudentz/zephyr,finikorg/zephyr,galak/zephyr,punitvara/zephyr,nashif/zephyr,GiulianoFranchetto/zephyr,zephyrproject-rtos/zephyr,punitvara/zephyr,finikorg/zephyr,explora26/zephyr,ldts/zephyr,finikorg/zephyr,kraj/zephyr,explora26/zephyr,explora26/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,nashif/zephyr,punitvara/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,punitvara/zephyr,ldts/zephyr,nashif/zephyr,Vudentz/zephyr,kraj/zephyr,zephyrproject-rtos/zephyr,GiulianoFranchetto/zephyr,galak/zephyr,kraj/zephyr,explora26/zephyr,ldts/zephyr,Vudentz/zephyr,GiulianoFranchetto/zephyr,punitvara/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,explora26/zephyr,kraj/zephyr,ldts/zephyr,Vudentz/zephyr,nashif/zephyr,GiulianoFranchetto/zephyr,finikorg/zephyr,nashif/zephyr,galak/zephyr,Vudentz/zephyr