Index out of range if directory not provided to webdav backend

init

#1

Please describe what you are doing to trigger the bug:
/Applications/Duplicacy.app/Contents/Resources/duplicacy_osx_x64_2.1.1 -d init test webdav://my_username@webdav.yandex.com

Please describe what you expect to happen (but doesn’t):
Successful initialization in the root folder of the yandex disk or the error message.

Please describe what actually happens (the wrong behaviour):

$ /Applications/Duplicacy.app/Contents/Resources/duplicacy_osx_x64_2.1.1  -d init test webdav://my_username@webdav.yandex.com
Reading the environment variable DUPLICACY_WEBDAV_PASSWORD
Enter the WebDAV password:password
runtime error: index out of range
goroutine 1 [running]:
runtime/debug.Stack(0x22, 0x0, 0x0)
	/usr/local/go/src/runtime/debug/stack.go:24 +0xa7
runtime/debug.PrintStack()
	/usr/local/go/src/runtime/debug/stack.go:16 +0x22
github.com/gilbertchen/duplicacy/src.CatchLogException()
	/Users/chgang/zincbox/go/src/github.com/gilbertchen/duplicacy/src/duplicacy_log.go:183 +0x189
panic(0x4848840, 0x4e99c50)
	/usr/local/go/src/runtime/panic.go:502 +0x229
github.com/gilbertchen/duplicacy/src.CreateWebDAVStorage(0x7ffeefbff921, 0x11, 0x0, 0x7ffeefbff915, 0xb, 0xc4200cc590, 0xe, 0x0, 0x0, 0x0, ...)
	/Users/chgang/zincbox/go/src/github.com/gilbertchen/duplicacy/src/duplicacy_webdavstorage.go:52 +0x633
github.com/gilbertchen/duplicacy/src.CreateStorage(0x4961240, 0x7, 0x7ffeefbff907, 0x4, 0x0, 0x0, 0x7ffeefbff90c, 0x26, 0x0, 0x0, ...)
	/Users/chgang/zincbox/go/src/github.com/gilbertchen/duplicacy/src/duplicacy_storage.go:625 +0x3c51
main.configRepository(0xc4200e50e0, 0xc4200e5001)
	/Users/chgang/zincbox/go/src/github.com/gilbertchen/duplicacy/duplicacy/duplicacy_main.go:318 +0x5b9
main.initRepository(0xc4200e50e0)
	/Users/chgang/zincbox/go/src/github.com/gilbertchen/duplicacy/duplicacy/duplicacy_main.go:213 +0x30
github.com/gilbertchen/duplicacy/vendor/github.com/gilbertchen/cli.Command.Run(0x495e758, 0x4, 0x0, 0x0, 0x0, 0x0, 0x0, 0x4990c36, 0x4f, 0x0, ...)
	/Users/chgang/zincbox/go/src/github.com/gilbertchen/duplicacy/vendor/github.com/gilbertchen/cli/command.go:160 +0x7ea
github.com/gilbertchen/duplicacy/vendor/github.com/gilbertchen/cli.(*App).Run(0xc4201ab7a0, 0xc4200d60f0, 0x5, 0x5, 0x0, 0x0)
	/Users/chgang/zincbox/go/src/github.com/gilbertchen/duplicacy/vendor/github.com/gilbertchen/cli/app.go:179 +0x864
main.main()
	/Users/chgang/zincbox/go/src/github.com/gilbertchen/duplicacy/duplicacy/duplicacy_main.go:2007 +0x57ab