Unable to access context menu for unsupported files

[EvHaus]

In my project I have some PDF files. I wanted to right-click on them from the project sidebar in Brackets and select the "Delete" option -- but a dialog comes up saying Brackets can't open the file. When I dismiss the dialog, the context menu is removed too.

I recommend not attempting to open files on right-click at all. But if that's too big a UX change, at least, provide a method to access the context menu.

[peterflynn]

Closing -- duplicate of #7676