Single file test runner doesn't accept theories with no data

  [FAIL] System.IO.Tests.Directory_Exists.UncPathWithoutShareNameAsPath_ReturnsFalse
  System.InvalidOperationException : No data found for System.IO.Tests.Directory_Exists.UncPathWithoutShareNameAsPath_ReturnsFalse


For some reason, this is not a problem for the xunit runner used outside single file scenario. Couldn't figure out the xunit voodoo to make it ignore this.