Allow creation of files that don't exist if the edit range is 0/0
Allow creation of files that don't exist if the edit range is 0/0

We can't calculate a range for a file that's not open and we don't want to create the file manually because it won't be atomic with the edits. We hope we'll never get edits for a new file that aren't at 0/0.

Fixes #339.

Dart-Code/Dart-Code,Dart-Code/Dart-Code,Dart-Code/Dart-Code,Dart-Code/Dart-Code,Dart-Code/Dart-Code