net: tcp: Recover a situation if the first net_buf is too short
net: tcp: Recover a situation if the first net_buf is too short

This is very unlikely to happen but the device will access null
pointer if we do not properly check the return value of header
check function.

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

kraj/zephyr,zephyrproject-rtos/zephyr,runchip/zephyr-cc3220,ldts/zephyr,zephyriot/zephyr,zephyrproject-rtos/zephyr,fbsder/zephyr,punitvara/zephyr,galak/zephyr,runchip/zephyr-cc3220,explora26/zephyr,kraj/zephyr,explora26/zephyr,Vudentz/zephyr,nashif/zephyr,galak/zephyr,punitvara/zephyr,runchip/zephyr-cc3220,mbolivar/zephyr,finikorg/zephyr,aceofall/zephyr-iotos,GiulianoFranchetto/zephyr,zephyrproject-rtos/zephyr,fbsder/zephyr,runchip/zephyr-cc3220,finikorg/zephyr,nashif/zephyr,explora26/zephyr,explora26/zephyr,punitvara/zephyr,Vudentz/zephyr,runchip/zephyr-cc3220,ldts/zephyr,kraj/zephyr,zephyriot/zephyr,zephyrproject-rtos/zephyr,zephyriot/zephyr,nashif/zephyr,mbolivar/zephyr,mbolivar/zephyr,Vudentz/zephyr,ldts/zephyr,punitvara/zephyr,Vudentz/zephyr,nashif/zephyr,galak/zephyr,GiulianoFranchetto/zephyr,nashif/zephyr,Vudentz/zephyr,finikorg/zephyr,zephyriot/zephyr,mbolivar/zephyr,aceofall/zephyr-iotos,zephyrproject-rtos/zephyr,GiulianoFranchetto/zephyr,finikorg/zephyr,galak/zephyr,punitvara/zephyr,galak/zephyr,fbsder/zephyr,finikorg/zephyr,explora26/zephyr,ldts/zephyr,mbolivar/zephyr,Vudentz/zephyr,fbsder/zephyr,aceofall/zephyr-iotos,GiulianoFranchetto/zephyr,kraj/zephyr,zephyriot/zephyr,aceofall/zephyr-iotos,kraj/zephyr,GiulianoFranchetto/zephyr,ldts/zephyr,fbsder/zephyr,aceofall/zephyr-iotos