Regression: ddev list, with appdir deleted, gives a panic

[rfay]

What happened (or feature request):

In #444 we made it possible to do a ddev list even if an app's directory was removed. Unfortunately there's been a regression and we're worse than we were before: Now we get a panic in this case.

$ ddev list
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x18 pc=0x1428df7]

goroutine 1 [running]:
github.com/drud/ddev/pkg/plugins/platform.GetApps(0x0)
	/go/src/github.com/drud/ddev/pkg/plugins/platform/utils.go:55 +0x3f7
github.com/drud/ddev/cmd/ddev/cmd.glob..func11(0x19a90a0, 0x19d57e0, 0x0, 0x0)
	/go/src/github.com/drud/ddev/cmd/ddev/cmd/list.go:17 +0x34
github.com/drud/ddev/vendor/github.com/spf13/cobra.(*Command).execute(0x19a90a0, 0x19d57e0, 0x0, 0x0, 0x19a90a0, 0x19d57e0)
	/go/src/github.com/drud/ddev/vendor/github.com/spf13/cobra/command.go:654 +0x2a2
github.com/drud/ddev/vendor/github.com/spf13/cobra.(*Command).ExecuteC(0x19a9be0, 0xc42001c0b8, 0x0, 0xc42013df48)
	/go/src/github.com/drud/ddev/vendor/github.com/spf13/cobra/command.go:729 +0x2fe
github.com/drud/ddev/vendor/github.com/spf13/cobra.(*Command).Execute(0x19a9be0, 0x0, 0x0)
	/go/src/github.com/drud/ddev/vendor/github.com/spf13/cobra/command.go:688 +0x2b
github.com/drud/ddev/cmd/ddev/cmd.Execute()
	/go/src/github.com/drud/ddev/cmd/ddev/cmd/root.go:105 +0x3b
main.main()
	/go/src/github.com/drud/ddev/cmd/ddev/main.go:6 +0x20

What you expected to happen:

How to reproduce this:

With current master, v0.9.3-3-g4ca6d38a (g4ca6d38a),

1. start an app,
2. remove its directory,
3. do a ddev list

Version: Please include the output of ddev version, docker version and the project's .ddev/config.yaml.

n$ ddev version
cli:       	v0.9.3-3-g4ca6d38a
web:       	drud/nginx-php-fpm-local:v0.8.0
db:        	drud/mysql-local-57:v0.6.2
dba:       	drud/phpmyadmin:v0.2.0
router:    	drud/ddev-router:v0.4.3
commit:    	v0.9.3-3-g4ca6d38a
build info:	Built Tue Oct 24 15:01:34 MDT 2017 rfay@Randy-Air.local drud/golang-build-container:v0.5.0

Anything else do we need to know:

Related source links or issues:

#444 was the issue where we solved this, and v0.9.3 doesn't have any trouble with it, so the regression is likely introduced in #495, the command-line config changes.

We also have a pending, nearly-done and highly-related PR in #460 which solves the problem for ddev rm and others.

I guess we probably need a test for this case if we're going to support it.

It looks to me like the panic is in platform.GetApps,

https://github.com/drud/ddev/blob/4ca6d38aa2158595160231fd3ac7aeec2501f3bc/pkg/plugins/platform/utils.go#L48-L56

When we try to assign to siteStruct.AppConfig.Name we get the panic.