[Coverity CID :195816]Null pointer dereferences in /tests/net/dhcpv4/src/main.c

[aasthagr]

Static code scan issues seen in File: /tests/net/dhcpv4/src/main.c
Category: Null pointer dereferences
Function: prepare_dhcp_offer
Component: Tests
CID: 195816
Please fix or provide comments to square it off in coverity in the link: https://scan9.coverity.com/reports.htm#v32951/p12996