"kdk update" runtime error when no configuration file is present

[raoulbhatia]

Running kdk update without a valid config file results in the following runtime error:
panic: runtime error: invalid memory address or nil pointer dereference.

kdk update                                                                                                                                            
WARN[0000] Failed to load KDK config.                    configFileUsed=/Users/user/.kdk/kdk/config.yaml err="open /Users/user/.kdk/kdk/config.yaml: no such file or directory"
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x90 pc=0x15fd04a]

goroutine 1 [running]:
github.com/cisco-sso/kdk/pkg/kdk.needsUpdateConfig(...)
	/home/travis/gopath/src/github.com/cisco-sso/kdk/pkg/kdk/update.go:81
github.com/cisco-sso/kdk/pkg/kdk.Update(0x1df1880)
	/home/travis/gopath/src/github.com/cisco-sso/kdk/pkg/kdk/update.go:94 +0x95a
github.com/cisco-sso/kdk/cmd/kdk.glob..func11(0x1de3de0, 0x1e0e5b8, 0x0, 0x0)
	/home/travis/gopath/src/github.com/cisco-sso/kdk/cmd/kdk/update.go:27 +0x2d
github.com/spf13/cobra.(*Command).execute(0x1de3de0, 0x1e0e5b8, 0x0, 0x0, 0x1de3de0, 0x1e0e5b8)
	/home/travis/gopath/pkg/mod/github.com/spf13/cobra@v0.0.3/command.go:766 +0x2aa
github.com/spf13/cobra.(*Command).ExecuteC(0x1de2880, 0xffffffffffffffff, 0x0, 0xc0004a9e08)
	/home/travis/gopath/pkg/mod/github.com/spf13/cobra@v0.0.3/command.go:852 +0x2ea
github.com/spf13/cobra.(*Command).Execute(...)
	/home/travis/gopath/pkg/mod/github.com/spf13/cobra@v0.0.3/command.go:800
github.com/cisco-sso/kdk/cmd/kdk.Execute()
	/home/travis/gopath/src/github.com/cisco-sso/kdk/cmd/kdk/kdk.go:49 +0x42
main.main()
	/home/travis/gopath/src/github.com/cisco-sso/kdk/main.go:20 +0x20