fix: stackit beta network-interface commands - add nil pointer checks and tests for the outputResult functions#605

marceljk merged 3 commits intomainstackitcloud/stackit-cli:mainfrom

fix/add-nil-pointer-checks-in-network-interfaces-commands-and-add-testsstackitcloud/stackit-cli:fix/add-nil-pointer-checks-in-network-interfaces-commands-and-add-testsCopy head branch name to clipboard