May throw error when stepping into file who's name is subset of a current file

[ivangreene]

autoload/vebugger/std.vim, line 205: bufwinnr(a:readResult.std.location.file) may erroneously return a value > -1 if a file currently open in the editor has a name that is a superset of the file being checked (which may not be open), causing sign to throw an error: Invalid buffer name: ...