Title bar bugged when no folder or file open and window.title has been customized

[pdavies]

• VSCode Version: Code 1.19.1 (0759f77, 2017-12-19T09:46:23.884Z)
• OS Version: Windows_NT x64 10.0.15063
• Extensions: Extensions are disabled

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Steps to Reproduce:

1. Set a custom window title, e.g. "window.title": "${dirty}${dirty}${activeEditorMedium} ${dirty}${dirty}${separator}${rootName}"
2. Close all tabs. If a folder/workspace is open, close that too, and close the Untitled-1 file that Code auto-opens.
3. The title bar should read Visual Studio Code. Instead, it reads index.html.