fix VS crash empty line tab indent in XAML

[nobushi95]

This pull request fix VS crash in XAML files when tab indenting at empty line.

When I tab indent at empty line in XAML files like below figure, Emacs Emulation throws an exception.

This problems occurs when indenting is None or Smart. [Text Editor] -> [XAML] -> [Tabs] -> [Indenting]

I fixed this problem by doing nothing when catching the exception.